diff --git a/02_Day_Data_types/02_day_data_types.md b/02_Day_Data_types/02_day_data_types.md index e27d43d..98960bf 100644 --- a/02_Day_Data_types/02_day_data_types.md +++ b/02_Day_Data_types/02_day_data_types.md @@ -7,10 +7,11 @@ Twitter Follow - Author: - Asabeneh Yetayeh
- January, 2020 - +Author: +Asabeneh Yetayeh
+ January, 2020 + + @@ -19,30 +20,30 @@ ![Thirty Days Of JavaScript](../images/banners/day_1_2.png) - [📔 Day 2](#-day-2) - - [Data Types](#data-types) - - [Primitive Data Types](#primitive-data-types) - - [Non-Primitive Data Types](#non-primitive-data-types) - - [Numbers](#numbers) - - [Declaring Number Data Types](#declaring-number-data-types) - - [Math Object](#math-object) - - [Random Number Generator](#random-number-generator) - - [Strings](#strings) - - [String Concatenation](#string-concatenation) - - [Concatenating Using Addition Operator](#concatenating-using-addition-operator) - - [Long Literal Strings](#long-literal-strings) - - [Escape Sequences in Strings](#escape-sequences-in-strings) - - [Template Literals (Template Strings)](#template-literals-template-strings) - - [String Methods](#string-methods) - - [Checking Data Types and Casting](#checking-data-types-and-casting) - - [Checking Data Types](#checking-data-types) - - [Changing Data Type (Casting)](#changing-data-type-casting) - - [String to Int](#string-to-int) - - [String to Float](#string-to-float) - - [Float to Int](#float-to-int) - - [💻 Day 2: Exercises](#-day-2-exercises) - - [Exercise: Level 1](#exercise-level-1) - - [Exercise: Level 2](#exercise-level-2) - - [Exercises: Level 3](#exercises-level-3) + - [Data Types](#data-types) + - [Primitive Data Types](#primitive-data-types) + - [Non-Primitive Data Types](#non-primitive-data-types) + - [Numbers](#numbers) + - [Declaring Number Data Types](#declaring-number-data-types) + - [Math Object](#math-object) + - [Random Number Generator](#random-number-generator) + - [Strings](#strings) + - [String Concatenation](#string-concatenation) + - [Concatenating Using Addition Operator](#concatenating-using-addition-operator) + - [Long Literal Strings](#long-literal-strings) + - [Escape Sequences in Strings](#escape-sequences-in-strings) + - [Template Literals (Template Strings)](#template-literals-template-strings) + - [String Methods](#string-methods) + - [Checking Data Types and Casting](#checking-data-types-and-casting) + - [Checking Data Types](#checking-data-types) + - [Changing Data Type (Casting)](#changing-data-type-casting) + - [String to Int](#string-to-int) + - [String to Float](#string-to-float) + - [Float to Int](#float-to-int) + - [💻 Day 2: Exercises](#-day-2-exercises) + - [Exercise: Level 1](#exercise-level-1) + - [Exercise: Level 2](#exercise-level-2) + - [Exercises: Level 3](#exercises-level-3) # 📔 Day 2 @@ -57,12 +58,12 @@ In the previous section, we mentioned a little bit about data types. Data or val Primitive data types in JavaScript include: - 1. Numbers - Integers, floats - 2. Strings - Any data under single quote, double quote or backtick quote - 3. Booleans - true or false value - 4. Null - empty value or no value - 5. Undefined - a declared variable without a value - 6. Symbol - A unique value that can be generated by Symbol constructor +1. Numbers - Integers, floats +2. Strings - Any data under single quote, double quote or backtick quote +3. Booleans - true or false value +4. Null - empty value or no value +5. Undefined - a declared variable without a value +6. Symbol - A unique value that can be generated by Symbol constructor Non-primitive data types in JavaScript includes: @@ -70,93 +71,93 @@ Non-primitive data types in JavaScript includes: 2. Arrays Now, let us see what exactly primitive and non-primitive data types mean. -*Primitive* data types are immutable(non-modifiable) data types. Once a primitive data type is created we cannot modify it. +_Primitive_ data types are immutable(non-modifiable) data types. Once a primitive data type is created we cannot modify it. **Example:** ```js -let word = 'JavaScript' +let word = "JavaScript"; ``` -If we try to modify the string stored in variable *word*, JavaScript should raise an error. Any data type under a single quote, double quote, or backtick quote is a string data type. +If we try to modify the string stored in variable _word_, JavaScript should raise an error. Any data type under a single quote, double quote, or backtick quote is a string data type. ```js -word[0] = 'Y' +word[0] = "Y"; ``` -This expression does not change the string stored in the variable *word*. So, we can say that strings are not modifiable or in other words immutable. +This expression does not change the string stored in the variable _word_. So, we can say that strings are not modifiable or in other words immutable. Primitive data types are compared by its values. Let us compare different data values. See the example below: ```js -let numOne = 3 -let numTwo = 3 +let numOne = 3; +let numTwo = 3; -console.log(numOne == numTwo) // true +console.log(numOne == numTwo); // true -let js = 'JavaScript' -let py = 'Python' +let js = "JavaScript"; +let py = "Python"; -console.log(js == py) //false +console.log(js == py); //false -let lightOn = true -let lightOff = false +let lightOn = true; +let lightOff = false; -console.log(lightOn == lightOff) // false +console.log(lightOn == lightOff); // false ``` ### Non-Primitive Data Types -*Non-primitive* data types are modifiable or mutable. We can modify the value of non-primitive data types after it gets created. +_Non-primitive_ data types are modifiable or mutable. We can modify the value of non-primitive data types after it gets created. Let us see by creating an array. An array is a list of data values in a square bracket. Arrays can contain the same or different data types. Array values are referenced by their index. In JavaScript array index starts at zero. I.e., the first element of an array is found at index zero, the second element at index one, and the third element at index two, etc. ```js -let nums = [1, 2, 3] -nums[0] = 10 +let nums = [1, 2, 3]; +nums[0] = 10; -console.log(nums) // [10, 2, 3] +console.log(nums); // [10, 2, 3] ``` As you can see, an array, which is a non-primitive data type is mutable. Non-primitive data types cannot be compared by value. Even if two non-primitive data types have the same properties and values, they are not strictly equal. ```js -let nums = [1, 2, 3] -let numbers = [1, 2, 3] +let nums = [1, 2, 3]; +let numbers = [1, 2, 3]; -console.log(nums == numbers) // false +console.log(nums == numbers); // false let userOne = { -name:'Asabeneh', -role:'teaching', -country:'Finland' -} + name: "Asabeneh", + role: "teaching", + country: "Finland", +}; let userTwo = { -name:'Asabeneh', -role:'teaching', -country:'Finland' -} + name: "Asabeneh", + role: "teaching", + country: "Finland", +}; -console.log(userOne == userTwo) // false +console.log(userOne == userTwo); // false ``` Rule of thumb, we do not compare non-primitive data types. Do not compare arrays, functions, or objects. Non-primitive values are referred to as reference types, because they are being compared by reference instead of value. Two objects are only strictly equal if they refer to the same underlying object. ```js -let nums = [1, 2, 3] -let numbers = nums +let nums = [1, 2, 3]; +let numbers = nums; -console.log(nums == numbers) // true +console.log(nums == numbers); // true let userOne = { -name:'Asabeneh', -role:'teaching', -country:'Finland' -} + name: "Asabeneh", + role: "teaching", + country: "Finland", +}; -let userTwo = userOne +let userTwo = userOne; -console.log(userOne == userTwo) // true +console.log(userOne == userTwo); // true ``` If you have a hard time understanding the difference between primitive data types and non-primitive data types, you are not the only one. Calm down and just go to the next section and try to come back after some time. Now let us start the data types by number type. @@ -169,16 +170,16 @@ Let's see some examples of Numbers. ### Declaring Number Data Types ```js -let age = 35 -const gravity = 9.81 // we use const for non-changing values, gravitational constant in m/s2 -let mass = 72 // mass in Kilogram -const PI = 3.14 // pi a geometrical constant +let age = 35; +const gravity = 9.81; // we use const for non-changing values, gravitational constant in m/s2 +let mass = 72; // mass in Kilogram +const PI = 3.14; // pi a geometrical constant // More Examples -const boilingPoint = 100 // temperature in oC, boiling point of water which is a constant -const bodyTemp = 37 // oC average human body temperature, which is a constant +const boilingPoint = 100; // temperature in oC, boiling point of water which is a constant +const bodyTemp = 37; // oC average human body temperature, which is a constant -console.log(age, gravity, mass, PI, boilingPoint, bodyTemp) +console.log(age, gravity, mass, PI, boilingPoint, bodyTemp); ``` ### Math Object @@ -186,98 +187,98 @@ console.log(age, gravity, mass, PI, boilingPoint, bodyTemp) In JavaScript the Math Object provides a lots of methods to work with numbers. ```js -const PI = Math.PI +const PI = Math.PI; -console.log(PI) // 3.141592653589793 +console.log(PI); // 3.141592653589793 // Rounding to the closest number // if above .5 up if less 0.5 down rounding -console.log(Math.round(PI)) // 3 to round values to the nearest number +console.log(Math.round(PI)); // 3 to round values to the nearest number -console.log(Math.round(9.81)) // 10 +console.log(Math.round(9.81)); // 10 -console.log(Math.floor(PI)) // 3 rounding down +console.log(Math.floor(PI)); // 3 rounding down -console.log(Math.ceil(PI)) // 4 rounding up +console.log(Math.ceil(PI)); // 4 rounding up -console.log(Math.min(-5, 3, 20, 4, 5, 10)) // -5, returns the minimum value +console.log(Math.min(-5, 3, 20, 4, 5, 10)); // -5, returns the minimum value -console.log(Math.max(-5, 3, 20, 4, 5, 10)) // 20, returns the maximum value +console.log(Math.max(-5, 3, 20, 4, 5, 10)); // 20, returns the maximum value -const randNum = Math.random() // creates random number between 0 to 0.999999 -console.log(randNum) +const randNum = Math.random(); // creates random number between 0 to 0.999999 +console.log(randNum); -// Let us create random number between 0 to 10 +// Let us create a random number between 0 to 10 -const num = Math.floor(Math.random () * 11) // creates random number between 0 and 10 -console.log(num) +const num = Math.floor(Math.random() * 11); // creates random number between 0 and 10 +console.log(num); //Absolute value -console.log(Math.abs(-10)) // 10 +console.log(Math.abs(-10)); // 10 //Square root -console.log(Math.sqrt(100)) // 10 +console.log(Math.sqrt(100)); // 10 -console.log(Math.sqrt(2)) // 1.4142135623730951 +console.log(Math.sqrt(2)); // 1.4142135623730951 // Power -console.log(Math.pow(3, 2)) // 9 +console.log(Math.pow(3, 2)); // 9 -console.log(Math.E) // 2.718 +console.log(Math.E); // 2.718 // Logarithm // Returns the natural logarithm with base E of x, Math.log(x) -console.log(Math.log(2)) // 0.6931471805599453 -console.log(Math.log(10)) // 2.302585092994046 +console.log(Math.log(2)); // 0.6931471805599453 +console.log(Math.log(10)); // 2.302585092994046 // Returns the natural logarithm of 2 and 10 respectively -console.log(Math.LN2) // 0.6931471805599453 -console.log(Math.LN10) // 2.302585092994046 +console.log(Math.LN2); // 0.6931471805599453 +console.log(Math.LN10); // 2.302585092994046 // Trigonometry -Math.sin(0) -Math.sin(60) +Math.sin(0); +Math.sin(60); -Math.cos(0) -Math.cos(60) +Math.cos(0); +Math.cos(60); ``` #### Random Number Generator -The JavaScript Math Object has a random() method number generator which generates number from 0 to 0.999999999... +The JavaScript Math Object has a random() method number generator which generates a number from 0 to 0.999999999... ```js -let randomNum = Math.random() // generates 0 to 0.999... +let randomNum = Math.random(); // generates 0 to 0.999... ``` Now, let us see how we can use random() method to generate a random number between 0 and 10: ```js -let randomNum = Math.random() // generates 0 to 0.999 -let numBtnZeroAndTen = randomNum * 11 +let randomNum = Math.random(); // generates 0 to 0.999 +let numBtnZeroAndTen = randomNum * 11; -console.log(numBtnZeroAndTen) // this gives: min 0 and max 10.99 +console.log(numBtnZeroAndTen); // this gives: min 0 and max 10.99 -let randomNumRoundToFloor = Math.floor(numBtnZeroAndTen) -console.log(randomNumRoundToFloor) // this gives between 0 and 10 +let randomNumRoundToFloor = Math.floor(numBtnZeroAndTen); +console.log(randomNumRoundToFloor); // this gives between 0 and 10 ``` ## Strings -Strings are texts, which are under **_single_** , **_double_**, **_back-tick_** quote. To declare a string, we need a variable name, assignment operator, a value under a single quote, double quote, or backtick quote. +Strings are texts, which are under **_single_** , **_double_**, **_back-tick_** quote. To declare a string, we need a variable name, assignment operator, a value under a single quote, double quote, or backtick quote. Let's see some examples of strings: ```js -let space = ' ' // an empty space string -let firstName = 'Asabeneh' -let lastName = 'Yetayeh' -let country = 'Finland' -let city = 'Helsinki' -let language = 'JavaScript' -let job = 'teacher' -let quote = "The saying,'Seeing is Believing' is not correct in 2020." -let quotWithBackTick = `The saying,'Seeing is Believing' is not correct in 2020.` +let space = " "; // an empty space string +let firstName = "Asabeneh"; +let lastName = "Yetayeh"; +let country = "Finland"; +let city = "Helsinki"; +let language = "JavaScript"; +let job = "teacher"; +let quote = "The saying,'Seeing is Believing' is not correct in 2020."; +let quotWithBackTick = `The saying,'Seeing is Believing' is not correct in 2020.`; ``` ### String Concatenation @@ -302,20 +303,19 @@ Concatenating using the addition operator is an old way. This way of concatenati ```js // Declaring different variables of different data types -let space = ' ' -let firstName = 'Asabeneh' -let lastName = 'Yetayeh' -let country = 'Finland' -let city = 'Helsinki' -let language = 'JavaScript' -let job = 'teacher' -let age = 250 - +let space = " "; +let firstName = "Asabeneh"; +let lastName = "Yetayeh"; +let country = "Finland"; +let city = "Helsinki"; +let language = "JavaScript"; +let job = "teacher"; +let age = 250; -let fullName =firstName + space + lastName -let personInfoOne = fullName + '. I am ' + age + '. I live in ' + country; // ES5 string addition +let fullName = firstName + space + lastName; +let personInfoOne = fullName + ". I am " + age + ". I live in " + country; // ES5 string addition -console.log(personInfoOne) +console.log(personInfoOne); ``` ```sh @@ -328,16 +328,17 @@ A string could be a single character or paragraph or a page. If the string lengt **Example:** ```js -const paragraph = "My name is Asabeneh Yetayeh. I live in Finland, Helsinki.\ +const paragraph = + "My name is Asabeneh Yetayeh. I live in Finland, Helsinki.\ I am a teacher and I love teaching. I teach HTML, CSS, JavaScript, React, Redux, \ Node.js, Python, Data Analysis and D3.js for anyone who is interested to learn. \ -In the end of 2019, I was thinking to expand my teaching and to reach \ +At the end of 2019, I was thinking to expand my teaching and to reach \ to global audience and I started a Python challenge from November 20 - December 19.\ It was one of the most rewarding and inspiring experience.\ Now, we are in 2020. I am enjoying preparing the 30DaysOfJavaScript challenge and \ -I hope you are enjoying too." +I hope you are enjoying too."; -console.log(paragraph) +console.log(paragraph); ``` #### Escape Sequences in Strings @@ -349,18 +350,20 @@ In JavaScript and other programming languages \ followed by some characters is a - \\\\: Back slash - \\': Single quote (') - \\": Double quote (") - + ```js -console.log('I hope everyone is enjoying the 30 Days Of JavaScript challenge.\nDo you ?') // line break -console.log('Days\tTopics\tExercises') -console.log('Day 1\t3\t5') -console.log('Day 2\t3\t5') -console.log('Day 3\t3\t5') -console.log('Day 4\t3\t5') -console.log('This is a backslash symbol (\\)') // To write a backslash -console.log('In every programming language it starts with \"Hello, World!\"') -console.log("In every programming language it starts with \'Hello, World!\'") -console.log('The saying \'Seeing is Believing\' isn\'t correct in 2020') +console.log( + "I hope everyone is enjoying the 30 Days Of JavaScript challenge.\nDo you ?" +); // line break +console.log("Days\tTopics\tExercises"); +console.log("Day 1\t3\t5"); +console.log("Day 2\t3\t5"); +console.log("Day 3\t3\t5"); +console.log("Day 4\t3\t5"); +console.log("This is a backslash symbol (\\)"); // To write a backslash +console.log('In every programming language it starts with "Hello, World!"'); +console.log("In every programming language it starts with 'Hello, World!'"); +console.log("The saying 'Seeing is Believing' isn't correct in 2020"); ``` Output in console: @@ -385,35 +388,34 @@ To create a template strings, we use two back-ticks. We can inject data as expre ```js //Syntax -`String literal text` -`String literal text ${expression}` +`String literal text``String literal text ${expression}`; ``` **Example: 1** ```js -console.log(`The sum of 2 and 3 is 5`) // statically writing the data -let a = 2 -let b = 3 -console.log(`The sum of ${a} and ${b} is ${a + b}`) // injecting the data dynamically +console.log(`The sum of 2 and 3 is 5`); // statically writing the data +let a = 2; +let b = 3; +console.log(`The sum of ${a} and ${b} is ${a + b}`); // injecting the data dynamically ``` **Example:2** ```js -let firstName = 'Asabeneh' -let lastName = 'Yetayeh' -let country = 'Finland' -let city = 'Helsinki' -let language = 'JavaScript' -let job = 'teacher' -let age = 250 -let fullName = firstName + ' ' + lastName +let firstName = "Asabeneh"; +let lastName = "Yetayeh"; +let country = "Finland"; +let city = "Helsinki"; +let language = "JavaScript"; +let job = "teacher"; +let age = 250; +let fullName = firstName + " " + lastName; -let personInfoTwo = `I am ${fullName}. I am ${age}. I live in ${country}.` //ES6 - String interpolation method -let personInfoThree = `I am ${fullName}. I live in ${city}, ${country}. I am a ${job}. I teach ${language}.` -console.log(personInfoTwo) -console.log(personInfoThree) +let personInfoTwo = `I am ${fullName}. I am ${age}. I live in ${country}.`; //ES6 - String interpolation method +let personInfoThree = `I am ${fullName}. I live in ${city}, ${country}. I am a ${job}. I teach ${language}.`; +console.log(personInfoTwo); +console.log(personInfoThree); ``` ```sh @@ -424,9 +426,9 @@ I am Asabeneh Yetayeh. I live in Helsinki, Finland. I am a teacher. I teach Java Using a string template or string interpolation method, we can add expressions, which could be a value, or some operations (comparison, arithmetic operations, ternary operation). ```js -let a = 2 -let b = 3 -console.log(`${a} is greater than ${b}: ${a > b}`) +let a = 2; +let b = 3; +console.log(`${a} is greater than ${b}: ${a > b}`); ``` ```sh @@ -437,321 +439,322 @@ console.log(`${a} is greater than ${b}: ${a > b}`) Everything in JavaScript is an object. A string is a primitive data type that means we can not modify it once it is created. The string object has many string methods. There are different string methods that can help us to work with strings. -1. *length*: The string *length* method returns the number of characters in a string included empty space. +1. _length_: The string _length_ method returns the number of characters in a string included empty space. **Example:** ```js -let js = 'JavaScript' -console.log(js.length) // 10 -let firstName = 'Asabeneh' -console.log(firstName.length) // 8 +let js = "JavaScript"; +console.log(js.length); // 10 +let firstName = "Asabeneh"; +console.log(firstName.length); // 8 ``` -2. *Accessing characters in a string*: We can access each character in a string using its index. In programming, counting starts from 0. The first index of the string is zero, and the last index is the length of the string minus one. +2. _Accessing characters in a string_: We can access each character in a string using its index. In programming, counting starts from 0. The first index of the string is zero, and the last index is the length of the string minus one. + +![Accessing sting by index](../images/string_indexes.png) - ![Accessing sting by index](../images/string_indexes.png) - Let us access different characters in 'JavaScript' string. ```js -let string = 'JavaScript' -let firstLetter = string[0] +let string = "JavaScript"; +let firstLetter = string[0]; -console.log(firstLetter) // J +console.log(firstLetter); // J -let secondLetter = string[1] // a -let thirdLetter = string[2] -let lastLetter = string[9] +let secondLetter = string[1]; // a +let thirdLetter = string[2]; +let lastLetter = string[9]; -console.log(lastLetter) // t +console.log(lastLetter); // t -let lastIndex = string.length - 1 +let lastIndex = string.length - 1; -console.log(lastIndex) // 9 -console.log(string[lastIndex]) // t +console.log(lastIndex); // 9 +console.log(string[lastIndex]); // t ``` -3. *toUpperCase()*: this method changes the string to uppercase letters. +3. _toUpperCase()_: this method changes the string to uppercase letters. ```js -let string = 'JavaScript' +let string = "JavaScript"; -console.log(string.toUpperCase()) // JAVASCRIPT +console.log(string.toUpperCase()); // JAVASCRIPT -let firstName = 'Asabeneh' +let firstName = "Asabeneh"; -console.log(firstName.toUpperCase()) // ASABENEH +console.log(firstName.toUpperCase()); // ASABENEH -let country = 'Finland' +let country = "Finland"; -console.log(country.toUpperCase()) // FINLAND +console.log(country.toUpperCase()); // FINLAND ``` -4. *toLowerCase()*: this method changes the string to lowercase letters. +4. _toLowerCase()_: this method changes the string to lowercase letters. ```js -let string = 'JavasCript' +let string = "JavasCript"; -console.log(string.toLowerCase()) // javascript +console.log(string.toLowerCase()); // javascript -let firstName = 'Asabeneh' +let firstName = "Asabeneh"; -console.log(firstName.toLowerCase()) // asabeneh +console.log(firstName.toLowerCase()); // asabeneh -let country = 'Finland' +let country = "Finland"; -console.log(country.toLowerCase()) // finland +console.log(country.toLowerCase()); // finland ``` -5. *substr()*: It takes two arguments, the starting index and number of characters to slice. +5. _substr()_: It takes two arguments, the starting index and number of characters to slice. ```js -let string = 'JavaScript' -console.log(string.substr(4,6)) // Script +let string = "JavaScript"; +console.log(string.substr(4, 6)); // Script -let country = 'Finland' -console.log(country.substr(3, 4)) // land +let country = "Finland"; +console.log(country.substr(3, 4)); // land ``` -6. *substring()*: It takes two arguments, the starting index and the stopping index but it doesn't include the character at the stopping index. +6. _substring()_: It takes two arguments, the starting index and the stopping index but it doesn't include the character at the stopping index. ```js -let string = 'JavaScript' +let string = "JavaScript"; -console.log(string.substring(0,4)) // Java -console.log(string.substring(4,10)) // Script -console.log(string.substring(4)) // Script +console.log(string.substring(0, 4)); // Java +console.log(string.substring(4, 10)); // Script +console.log(string.substring(4)); // Script -let country = 'Finland' +let country = "Finland"; -console.log(country.substring(0, 3)) // Fin -console.log(country.substring(3, 7)) // land -console.log(country.substring(3)) // land +console.log(country.substring(0, 3)); // Fin +console.log(country.substring(3, 7)); // land +console.log(country.substring(3)); // land ``` -7. *split()*: The split method splits a string at a specified place. +7. _split()_: The split method splits a string at a specified place. ```js -let string = '30 Days Of JavaScript' +let string = "30 Days Of JavaScript"; -console.log(string.split()) // Changes to an array -> ["30 Days Of JavaScript"] -console.log(string.split(' ')) // Split to an array at space -> ["30", "Days", "Of", "JavaScript"] +console.log(string.split()); // Changes to an array -> ["30 Days Of JavaScript"] +console.log(string.split(" ")); // Split to an array at space -> ["30", "Days", "Of", "JavaScript"] -let firstName = 'Asabeneh' +let firstName = "Asabeneh"; -console.log(firstName.split()) // Change to an array - > ["Asabeneh"] -console.log(firstName.split('')) // Split to an array at each letter -> ["A", "s", "a", "b", "e", "n", "e", "h"] +console.log(firstName.split()); // Change to an array - > ["Asabeneh"] +console.log(firstName.split("")); // Split to an array at each letter -> ["A", "s", "a", "b", "e", "n", "e", "h"] -let countries = 'Finland, Sweden, Norway, Denmark, and Iceland' +let countries = "Finland, Sweden, Norway, Denmark, and Iceland"; -console.log(countries.split(',')) // split to any array at comma -> ["Finland", " Sweden", " Norway", " Denmark", " and Iceland"] -console.log(countries.split(', ')) //  ["Finland", "Sweden", "Norway", "Denmark", "and Iceland"] +console.log(countries.split(",")); // split to any array at comma -> ["Finland", " Sweden", " Norway", " Denmark", " and Iceland"] +console.log(countries.split(", ")); //  ["Finland", "Sweden", "Norway", "Denmark", "and Iceland"] ``` -8. *trim()*: Removes trailing space in the beginning or the end of a string. +8. _trim()_: Removes trailing space in the beginning or the end of a string. ```js -let string = ' 30 Days Of JavaScript ' +let string = " 30 Days Of JavaScript "; -console.log(string) -console.log(string.trim(' ')) +console.log(string); +console.log(string.trim(" ")); -let firstName = ' Asabeneh ' +let firstName = " Asabeneh "; -console.log(firstName) -console.log(firstName.trim()) // still removes spaces at the beginning and the end of the string +console.log(firstName); +console.log(firstName.trim()); // still removes spaces at the beginning and the end of the string ``` ```sh - 30 Days Of JavasCript + 30 Days Of JavasCript 30 Days Of JavasCript - Asabeneh + Asabeneh Asabeneh ``` -9. *includes()*: It takes a substring argument and it checks if substring argument exists in the string. *includes()* returns a boolean. If a substring exist in a string, it returns true, otherwise it returns false. +9. _includes()_: It takes a substring argument and it checks if substring argument exists in the string. _includes()_ returns a boolean. If a substring exist in a string, it returns true, otherwise it returns false. ```js -let string = '30 Days Of JavaScript' +let string = "30 Days Of JavaScript"; -console.log(string.includes('Days')) // true -console.log(string.includes('days')) // false - it is case sensitive! -console.log(string.includes('Script')) // true -console.log(string.includes('script')) // false -console.log(string.includes('java')) // false -console.log(string.includes('Java')) // true +console.log(string.includes("Days")); // true +console.log(string.includes("days")); // false - it is case sensitive! +console.log(string.includes("Script")); // true +console.log(string.includes("script")); // false +console.log(string.includes("java")); // false +console.log(string.includes("Java")); // true -let country = 'Finland' +let country = "Finland"; -console.log(country.includes('fin')) // false -console.log(country.includes('Fin')) // true -console.log(country.includes('land')) // true -console.log(country.includes('Land')) // false +console.log(country.includes("fin")); // false +console.log(country.includes("Fin")); // true +console.log(country.includes("land")); // true +console.log(country.includes("Land")); // false ``` -10. *replace()*: takes as a parameter the old substring and a new substring. +10. _replace()_: takes as a parameter the old substring and a new substring. ```js -string.replace(oldsubstring, newsubstring) +string.replace(oldsubstring, newsubstring); ``` ```js -let string = '30 Days Of JavaScript' -console.log(string.replace('JavaScript', 'Python')) // 30 Days Of Python +let string = "30 Days Of JavaScript"; +console.log(string.replace("JavaScript", "Python")); // 30 Days Of Python -let country = 'Finland' -console.log(country.replace('Fin', 'Noman')) // Nomanland +let country = "Finland"; +console.log(country.replace("Fin", "Noman")); // Nomanland ``` -11. *charAt()*: Takes index and it returns the value at that index +11. _charAt()_: Takes index and it returns the value at that index ```js -string.charAt(index) +string.charAt(index); ``` ```js -let string = '30 Days Of JavaScript' -console.log(string.charAt(0)) // 3 +let string = "30 Days Of JavaScript"; +console.log(string.charAt(0)); // 3 -let lastIndex = string.length - 1 -console.log(string.charAt(lastIndex)) // t +let lastIndex = string.length - 1; +console.log(string.charAt(lastIndex)); // t ``` -12. *charCodeAt()*: Takes index and it returns char code (ASCII number) of the value at that index +12. _charCodeAt()_: Takes index and it returns char code (ASCII number) of the value at that index ```js -string.charCodeAt(index) +string.charCodeAt(index); ``` ```js -let string = '30 Days Of JavaScript' -console.log(string.charCodeAt(3)) // D ASCII number is 68 - -let lastIndex = string.length - 1 -console.log(string.charCodeAt(lastIndex)) // t ASCII is 116 +let string = "30 Days Of JavaScript"; +console.log(string.charCodeAt(3)); // D ASCII number is 68 +let lastIndex = string.length - 1; +console.log(string.charCodeAt(lastIndex)); // t ASCII is 116 ``` -13. *indexOf()*: Takes a substring and if the substring exists in a string it returns the first position of the substring if does not exist it returns -1 +13. _indexOf()_: Takes a substring and if the substring exists in a string it returns the first position of the substring if does not exist it returns -1 ```js -string.indexOf(substring) +string.indexOf(substring); ``` ```js -let string = '30 Days Of JavaScript' +let string = "30 Days Of JavaScript"; -console.log(string.indexOf('D')) // 3 -console.log(string.indexOf('Days')) // 3 -console.log(string.indexOf('days')) // -1 -console.log(string.indexOf('a')) // 4 -console.log(string.indexOf('JavaScript')) // 11 -console.log(string.indexOf('Script')) //15 -console.log(string.indexOf('script')) // -1 +console.log(string.indexOf("D")); // 3 +console.log(string.indexOf("Days")); // 3 +console.log(string.indexOf("days")); // -1 +console.log(string.indexOf("a")); // 4 +console.log(string.indexOf("JavaScript")); // 11 +console.log(string.indexOf("Script")); //15 +console.log(string.indexOf("script")); // -1 ``` -14. *lastIndexOf()*: Takes a substring and if the substring exists in a string it returns the last position of the substring if it does not exist it returns -1 - +14. _lastIndexOf()_: Takes a substring and if the substring exists in a string it returns the last position of the substring if it does not exist it returns -1 ```js //syntax -string.lastIndexOf(substring) +string.lastIndexOf(substring); ``` ```js -let string = 'I love JavaScript. If you do not love JavaScript what else can you love.' +let string = + "I love JavaScript. If you do not love JavaScript what else can you love."; -console.log(string.lastIndexOf('love')) // 67 -console.log(string.lastIndexOf('you')) // 63 -console.log(string.lastIndexOf('JavaScript')) // 38 +console.log(string.lastIndexOf("love")); // 67 +console.log(string.lastIndexOf("you")); // 63 +console.log(string.lastIndexOf("JavaScript")); // 38 ``` -15. *concat()*: it takes many substrings and joins them. +15. _concat()_: it takes many substrings and joins them. ```js -string.concat(substring, substring, substring) +string.concat(substring, substring, substring); ``` ```js -let string = '30' -console.log(string.concat("Days", "Of", "JavaScript")) // 30DaysOfJavaScript +let string = "30"; +console.log(string.concat("Days", "Of", "JavaScript")); // 30DaysOfJavaScript -let country = 'Fin' -console.log(country.concat("land")) // Finland +let country = "Fin"; +console.log(country.concat("land")); // Finland ``` -16. *startsWith*: it takes a substring as an argument and it checks if the string starts with that specified substring. It returns a boolean(true or false). +16. _startsWith_: it takes a substring as an argument and it checks if the string starts with that specified substring. It returns a boolean(true or false). ```js //syntax -string.startsWith(substring) +string.startsWith(substring); ``` ```js -let string = 'Love is the best to in this world' +let string = "Love is the best to in this world"; -console.log(string.startsWith('Love')) // true -console.log(string.startsWith('love')) // false -console.log(string.startsWith('world')) // false +console.log(string.startsWith("Love")); // true +console.log(string.startsWith("love")); // false +console.log(string.startsWith("world")); // false -let country = 'Finland' +let country = "Finland"; -console.log(country.startsWith('Fin')) // true -console.log(country.startsWith('fin')) // false -console.log(country.startsWith('land')) // false +console.log(country.startsWith("Fin")); // true +console.log(country.startsWith("fin")); // false +console.log(country.startsWith("land")); // false ``` -17. *endsWith*: it takes a substring as an argument and it checks if the string ends with that specified substring. It returns a boolean(true or false). +17. _endsWith_: it takes a substring as an argument and it checks if the string ends with that specified substring. It returns a boolean(true or false). ```js -string.endsWith(substring) +string.endsWith(substring); ``` ```js -let string = 'Love is the most powerful feeling in the world' +let string = "Love is the most powerful feeling in the world"; -console.log(string.endsWith('world')) // true -console.log(string.endsWith('love')) // false -console.log(string.endsWith('in the world')) // true +console.log(string.endsWith("world")); // true +console.log(string.endsWith("love")); // false +console.log(string.endsWith("in the world")); // true -let country = 'Finland' +let country = "Finland"; -console.log(country.endsWith('land')) // true -console.log(country.endsWith('fin')) // false -console.log(country.endsWith('Fin')) // false +console.log(country.endsWith("land")); // true +console.log(country.endsWith("fin")); // false +console.log(country.endsWith("Fin")); // false ``` -18. *search*: it takes a substring as an argument and it returns the index of the first match. The search value can be a string or a regular expression pattern. +18. _search_: it takes a substring as an argument and it returns the index of the first match. The search value can be a string or a regular expression pattern. ```js -string.search(substring) +string.search(substring); ``` ```js -let string = 'I love JavaScript. If you do not love JavaScript what else can you love.' -console.log(string.search('love')) // 2 -console.log(string.search(/javascript/gi)) // 7 +let string = + "I love JavaScript. If you do not love JavaScript what else can you love."; +console.log(string.search("love")); // 2 +console.log(string.search(/javascript/gi)); // 7 ``` -19. *match*: it takes a substring or regular expression pattern as an argument and it returns an array if there is match if not it returns null. Let us see how a regular expression pattern looks like. It starts with / sign and ends with / sign. +19. _match_: it takes a substring or regular expression pattern as an argument and it returns an array if there is match if not it returns null. Let us see how a regular expression pattern looks like. It starts with / sign and ends with / sign. ```js -let string = 'love' -let patternOne = /love/ // with out any flag -let patternTwo = /love/gi // g-means to search in the whole text, i - case insensitive +let string = "love"; +let patternOne = /love/; // with out any flag +let patternTwo = /love/gi; // g-means to search in the whole text, i - case insensitive ``` Match syntax ```js // syntax -string.match(substring) +string.match(substring); ``` ```js -let string = 'I love JavaScript. If you do not love JavaScript what else can you love.' -console.log(string.match('love')) +let string = + "I love JavaScript. If you do not love JavaScript what else can you love."; +console.log(string.match("love")); ``` ```sh @@ -759,33 +762,34 @@ console.log(string.match('love')) ``` ```js -let pattern = /love/gi -console.log(string.match(pattern)) // ["love", "love", "love"] +let pattern = /love/gi; +console.log(string.match(pattern)); // ["love", "love", "love"] ``` Let us extract numbers from text using a regular expression. This is not the regular expression section, do not panic! We will cover regular expressions later on. ```js -let txt = 'In 2019, I ran 30 Days of Python. Now, in 2020 I am super exited to start this challenge' -let regEx = /\d+/ +let txt = + "In 2019, I ran 30 Days of Python. Now, in 2020 I am super exited to start this challenge"; +let regEx = /\d+/; // d with escape character means d not a normal d instead acts a digit // + means one or more digit numbers, // if there is g after that it means global, search everywhere. -console.log(txt.match(regEx)) // ["2", "0", "1", "9", "3", "0", "2", "0", "2", "0"] -console.log(txt.match(/\d+/g)) // ["2019", "30", "2020"] +console.log(txt.match(regEx)); // ["2", "0", "1", "9", "3", "0", "2", "0", "2", "0"] +console.log(txt.match(/\d+/g)); // ["2019", "30", "2020"] ``` -20. *repeat()*: it takes a number as argument and it returns the repeated version of the string. +20. _repeat()_: it takes a number as argument and it returns the repeated version of the string. ```js -string.repeat(n) +string.repeat(n); ``` ```js -let string = 'love' -console.log(string.repeat(10)) // lovelovelovelovelovelovelovelovelovelove +let string = "love"; +console.log(string.repeat(10)); // lovelovelovelovelovelovelovelovelovelove ``` ## Checking Data Types and Casting @@ -800,23 +804,23 @@ To check the data type of a certain variable we use the _typeof_ method. // Different javascript data types // Let's declare different data types -let firstName = 'Asabeneh' // string -let lastName = 'Yetayeh' // string -let country = 'Finland' // string -let city = 'Helsinki' // string -let age = 250 // number, it is not my real age, do not worry about it -let job // undefined, because a value was not assigned - -console.log(typeof 'Asabeneh') // string -console.log(typeof firstName) // string -console.log(typeof 10) // number -console.log(typeof 3.14) // number -console.log(typeof true) // boolean -console.log(typeof false) // boolean -console.log(typeof NaN) // number -console.log(typeof job) // undefined -console.log(typeof undefined) // undefined -console.log(typeof null) // object +let firstName = "Asabeneh"; // string +let lastName = "Yetayeh"; // string +let country = "Finland"; // string +let city = "Helsinki"; // string +let age = 250; // number, it is not my real age, do not worry about it +let job; // undefined, because a value was not assigned + +console.log(typeof "Asabeneh"); // string +console.log(typeof firstName); // string +console.log(typeof 10); // number +console.log(typeof 3.14); // number +console.log(typeof true); // boolean +console.log(typeof false); // boolean +console.log(typeof NaN); // number +console.log(typeof job); // undefined +console.log(typeof undefined); // undefined +console.log(typeof null); // object ``` ### Changing Data Type (Casting) @@ -834,23 +838,23 @@ We can convert string to number using the following methods: - Plus sign(+) ```js -let num = '10' -let numInt = parseInt(num) -console.log(numInt) // 10 +let num = "10"; +let numInt = parseInt(num); +console.log(numInt); // 10 ``` ```js -let num = '10' -let numInt = Number(num) +let num = "10"; +let numInt = Number(num); -console.log(numInt) // 10 +console.log(numInt); // 10 ``` ```js -let num = '10' -let numInt = +num +let num = "10"; +let numInt = +num; -console.log(numInt) // 10 +console.log(numInt); // 10 ``` #### String to Float @@ -863,24 +867,24 @@ We can convert string float to number using the following methods: - Plus sign(+) ```js -let num = '9.81' -let numFloat = parseFloat(num) +let num = "9.81"; +let numFloat = parseFloat(num); -console.log(numFloat) // 9.81 +console.log(numFloat); // 9.81 ``` ```js -let num = '9.81' -let numFloat = Number(num) +let num = "9.81"; +let numFloat = Number(num); -console.log(numFloat) // 9.81 +console.log(numFloat); // 9.81 ``` ```js -let num = '9.81' -let numFloat = +num +let num = "9.81"; +let numFloat = +num; -console.log(numFloat) // 9.81 +console.log(numFloat); // 9.81 ``` #### Float to Int @@ -889,59 +893,59 @@ We can convert float numbers to integers. We use the following method to convert float to int: - parseInt() - + ```js -let num = 9.81 -let numInt = parseInt(num) +let num = 9.81; +let numInt = parseInt(num); -console.log(numInt) // 9 +console.log(numInt); // 9 ``` -🌕 You are awesome. You have just completed day 2 challenges and you are two steps ahead on your way to greatness. Now do some exercises for your brain and for your muscle. +🌕 You are awesome. You have just completed day 2 challenges and you are two steps ahead on your way to greatness. Now do some exercises for your brain and for your muscle. ## 💻 Day 2: Exercises ### Exercise: Level 1 1. Declare a variable named challenge and assign it to an initial value **'30 Days Of JavaScript'**. -2. Print the string on the browser console using __console.log()__ -3. Print the __length__ of the string on the browser console using _console.log()_ -4. Change all the string characters to capital letters using __toUpperCase()__ method -5. Change all the string characters to lowercase letters using __toLowerCase()__ method -6. Cut (slice) out the first word of the string using __substr()__ or __substring()__ method -7. Slice out the phrase *Days Of JavaScript* from *30 Days Of JavaScript*. -8. Check if the string contains a word __Script__ using __includes()__ method -9. Split the __string__ into an __array__ using __split()__ method -10. Split the string 30 Days Of JavaScript at the space using __split()__ method -11. 'Facebook, Google, Microsoft, Apple, IBM, Oracle, Amazon' __split__ the string at the comma and change it to an array. -12. Change 30 Days Of JavaScript to 30 Days Of Python using __replace()__ method. -13. What is character at index 15 in '30 Days Of JavaScript' string? Use __charAt()__ method. -14. What is the character code of J in '30 Days Of JavaScript' string using __charCodeAt()__ -15. Use __indexOf__ to determine the position of the first occurrence of __a__ in 30 Days Of JavaScript -16. Use __lastIndexOf__ to determine the position of the last occurrence of __a__ in 30 Days Of JavaScript. -17. Use __indexOf__ to find the position of the first occurrence of the word __because__ in the following sentence:__'You cannot end a sentence with because because because is a conjunction'__ -18. Use __lastIndexOf__ to find the position of the last occurrence of the word __because__ in the following sentence:__'You cannot end a sentence with because because because is a conjunction'__ -19. Use __search__ to find the position of the first occurrence of the word __because__ in the following sentence:__'You cannot end a sentence with because because because is a conjunction'__ -20. Use __trim()__ to remove any trailing whitespace at the beginning and the end of a string.E.g ' 30 Days Of JavaScript '. -21. Use __startsWith()__ method with the string *30 Days Of JavaScript* and make the result true -22. Use __endsWith()__ method with the string *30 Days Of JavaScript* and make the result true -23. Use __match()__ method to find all the __a__’s in 30 Days Of JavaScript -24. Use __concat()__ and merge '30 Days of' and 'JavaScript' to a single string, '30 Days Of JavaScript' -25. Use __repeat()__ method to print 30 Days Of JavaScript 2 times +2. Print the string on the browser console using **console.log()** +3. Print the **length** of the string on the browser console using _console.log()_ +4. Change all the string characters to capital letters using **toUpperCase()** method +5. Change all the string characters to lowercase letters using **toLowerCase()** method +6. Cut (slice) out the first word of the string using **substr()** or **substring()** method +7. Slice out the phrase _Days Of JavaScript_ from _30 Days Of JavaScript_. +8. Check if the string contains a word **Script** using **includes()** method +9. Split the **string** into an **array** using **split()** method +10. Split the string 30 Days Of JavaScript at the space using **split()** method +11. 'Facebook, Google, Microsoft, Apple, IBM, Oracle, Amazon' **split** the string at the comma and change it to an array. +12. Change 30 Days Of JavaScript to 30 Days Of Python using **replace()** method. +13. What is character at index 15 in '30 Days Of JavaScript' string? Use **charAt()** method. +14. What is the character code of J in '30 Days Of JavaScript' string using **charCodeAt()** +15. Use **indexOf** to determine the position of the first occurrence of **a** in 30 Days Of JavaScript +16. Use **lastIndexOf** to determine the position of the last occurrence of **a** in 30 Days Of JavaScript. +17. Use **indexOf** to find the position of the first occurrence of the word **because** in the following sentence:**'You cannot end a sentence with because because because is a conjunction'** +18. Use **lastIndexOf** to find the position of the last occurrence of the word **because** in the following sentence:**'You cannot end a sentence with because because because is a conjunction'** +19. Use **search** to find the position of the first occurrence of the word **because** in the following sentence:**'You cannot end a sentence with because because because is a conjunction'** +20. Use **trim()** to remove any trailing whitespace at the beginning and the end of a string.E.g ' 30 Days Of JavaScript '. +21. Use **startsWith()** method with the string _30 Days Of JavaScript_ and make the result true +22. Use **endsWith()** method with the string _30 Days Of JavaScript_ and make the result true +23. Use **match()** method to find all the **a**’s in 30 Days Of JavaScript +24. Use **concat()** and merge '30 Days of' and 'JavaScript' to a single string, '30 Days Of JavaScript' +25. Use **repeat()** method to print 30 Days Of JavaScript 2 times ### Exercise: Level 2 1. Using console.log() print out the following statement: - ```sh - The quote 'There is no exercise better for the heart than reaching down and lifting people up.' by John Holmes teaches us to help one another. - ``` + ```sh + The quote 'There is no exercise better for the heart than reaching down and lifting people up.' by John Holmes teaches us to help one another. + ``` 2. Using console.log() print out the following quote by Mother Teresa: - ```sh - "Love is not patronizing and charity isn't about pity, it is about love. Charity and love are the same -- with charity you give love, so don't just give money but reach out your hand instead." - ``` + ```sh + "Love is not patronizing and charity isn't about pity, it is about love. Charity and love are the same -- with charity you give love, so don't just give money but reach out your hand instead." + ``` 3. Check if typeof '10' is exactly equal to 10. If not make it exactly equal. 4. Check if parseFloat('9.8') is equal to 10 if not make it exactly equal with 10. @@ -961,17 +965,18 @@ console.log(numInt) // 9 5 1 5 25 125 ``` -12. Use __substr__ to slice out the phrase __because because because__ from the following sentence:__'You cannot end a sentence with because because because is a conjunction'__ +12. Use **substr** to slice out the phrase **because because because** from the following sentence:**'You cannot end a sentence with because because because is a conjunction'** ### Exercises: Level 3 -1. 'Love is the best thing in this world. Some found their love and some are still looking for their love.' Count the number of word __love__ in this sentence. -2. Use __match()__ to count the number of all __because__ in the following sentence:__'You cannot end a sentence with because because because is a conjunction'__ +1. 'Love is the best thing in this world. Some found their love and some are still looking for their love.' Count the number of words **love** in this sentence. +2. Use **match()** to count the number of all **because** in the following sentence:**'You cannot end a sentence with because because because is a conjunction'** 3. Clean the following text and find the most frequent word (hint, use replace and regular expressions). - ```js - const sentence = '%I $am@% a %tea@cher%, &and& I lo%#ve %te@a@ching%;. The@re $is no@th@ing; &as& mo@re rewarding as educa@ting &and& @emp%o@weri@ng peo@ple. ;I found tea@ching m%o@re interesting tha@n any ot#her %jo@bs. %Do@es thi%s mo@tiv#ate yo@u to be a tea@cher!? %Th#is 30#Days&OfJavaScript &is al@so $the $resu@lt of &love& of tea&ching' - ``` + ```js + const sentence = + "%I $am@% a %tea@cher%, &and& I lo%#ve %te@a@ching%;. The@re $is no@th@ing; &as& mo@re rewarding as educa@ting &and& @emp%o@weri@ng peo@ple. ;I found tea@ching m%o@re interesting tha@n any ot#her %jo@bs. %Do@es thi%s mo@tiv#ate yo@u to be a tea@cher!? %Th#is 30#Days&OfJavaScript &is al@so $the $resu@lt of &love& of tea&ching"; + ``` 4. Calculate the total annual income of the person by extracting the numbers from the following text. 'He earns 5000 euro from salary per month, 10000 euro annual bonus, 15000 euro online courses per month.'