In the previous section, we mentioned a little bit about data types. Data or values have data types. Data types describe the characteristics of data. Data types can be divided into two:
In the previous section, we mentioned a little bit about data types. Data or values have data types. Data types describe the characteristics of data. Data types can be divided into two categories:
1. Primitive data types
2. Non-primitive data types(Object References)
@ -159,7 +159,7 @@ let userTwo = userOne
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.
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 explore the details of data types starting with numbers.
In JavaScript the Math Object provides a lots of methods to work with numbers.
In JavaScript the Math Object provides lots of methods to work with numbers.
```js
const PI = Math.PI
@ -381,7 +381,7 @@ The saying 'Seeing is Believing' isn't correct in 2020
#### Template Literals (Template Strings)
To create a template strings, we use two back-ticks. We can inject data as expressions inside a template string. To inject data, we enclose the expression with a curly bracket({}) preceded by a $ sign. See the syntax below.
To create template strings, we use two back-ticks. We can inject data as expressions inside a template string. To inject data, we enclose the expression with a curly bracket({}) preceded by a $ sign. See the syntax below.
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 what a regular expression pattern looks like. It starts with / sign and ends with / sign.
A boolean data type represents one of the two values:_true_ or _false_. Boolean value is either true or false. The use of these data types will be clear when you start the comparison operator. Any comparisons return a boolean value which is either true or false.
A boolean data type represents one of the two values:_true_ or _false_. Boolean value is either true or false. The use of these data types will be clear when you start using comparison operators. Any comparisons return a boolean value which is either true or false.
**Example: Boolean Values**
@ -86,7 +86,7 @@ We agreed that boolean values are either true or false.
- the boolean false
- '', "", ``, empty string
It is good to remember those truthy values and falsy values. In later section, we will use them with conditions to make decisions.
It is good to remember those truthy values and falsy values. In a later section, we will use them with conditions to make decisions.
Try to understand the above comparisons with some logic. Remembering without any logic might be difficult.
JavaScript is somehow a wired kind of programming language. JavaScript code run and give you a result but unless you are good at it may not be the desired result.
JavaScript is somehow a wired kind of programming language. JavaScript code runs and gives you a result but unless you are good at it may not be the desired result.
As rule of thumb, if a value is not true with == it will not be equal with ===. Using === is safer than using ==. The following [link](https://dorey.github.io/JavaScript-Equality-Table/) has an exhaustive list of comparison of data types.
@ -272,7 +272,7 @@ console.log(count++) // 0
console.log(count) // 1
```
We use most of the time post-increment. At least you should remember how to use post-increment operator.
Most of the time we use post-increment. At least you should remember how to use post-increment operator.
### Decrement Operator
@ -351,7 +351,7 @@ alert(message)
alert('Welcome to 30DaysOfJavaScript')
```
Do not use too much alert because it is destructing and annoying, use it just to test.
Do not use too much alert because it is distracting and annoying, use it just to test.
🌕 You have boundless energy. You have just completed day 3 challenges and you are three steps ahead in to your way to greatness. Now do some exercises for your brain and for your muscle.
🌕 You have boundless energy. You have just completed day 3 challenges and you are three steps ahead on your way to greatness. Now do some exercises for your brain and for your muscle.
1. Write a script that prompt the user to enter side a, side b, and side c of the triangle and and calculate the perimeter of triangle (perimeter = a + b + c)
1. Write a script that prompts the user to enter side a, side b, and side c of the triangle and and calculate the perimeter of triangle (perimeter = a + b + c)
1. Create a human readable time format using the Date time object. The hour and the minute should be all the time two digits(7 hours should be 07 and 5 minutes should be 05 )
1. YYY-MM-DD HH:mm eg. 20120-01-02 07:05
1. YYYY-MM-DD HH:mm eg. 2012-01-02 07:05
[<< Day 2](../02_Day_Data_types/02_day_data_types.md) | [Day 4 >>](../04_Day_Conditionals/04_day_conditionals.md)
Conditional statements are used for make decisions based on different conditions.
By default , statements in JavaScript script executed sequentially from top to bottom. If the processing logic require so, the sequential flow of execution can be altered in two ways:
Conditional statements are used for making decisions based on different conditions.
By default , statements in JavaScript execute sequentially from top to bottom. If the processing logic require so, the sequential flow of execution can be altered in two ways:
- Conditional execution: a block of one or more statements will be executed if a certain expression is true
- Repetitive execution: a block of one or more statements will be repetitively executed as long as a certain expression is true. In this section, we will cover _if_, _else_ , _else if_ statements. The comparison and logical operators we learned in the previous sections will be useful in here.
@ -49,7 +49,7 @@ Conditions can be implementing using the following ways:
### If
In JavaScript and other programming languages the key word _if_ is to used check if a condition is true and to execute the block code. To create an if condition, we need _if_ keyword, condition inside a parenthesis and block of code inside a curly bracket({}).
In JavaScript and other programming languages the key word _if_ is to used check if a condition is true and to execute the block of code. To create an if condition, we need _if_ keyword, condition inside a parenthesis and a block of code inside a curly bracket({}).
```js
// syntax
@ -324,7 +324,7 @@ isRaining
### Exercises: Level 2
1. Write a code which can give grades to students according to theirs scores:
🌕 You are diligent and you have already achieved quite a lot. You have just completed day 5 challenges and you are 5 steps ahead in to your way to greatness. Now do some exercises for your brain and for your muscle.
🌕 You are diligent and you have already achieved quite a lot. You have just completed day 5 challenges and you are 5 steps ahead on your way to greatness. Now do some exercises for your brain and for your muscle.
## 💻 Exercise
### Exercise: Level 1
```js
const countries = [
'Albania',
'Bolivia',
'Canada',
'Denmark',
'Ethiopia',
'Finland',
'Germany',
'Hungary',
'Ireland',
'Japan',
'Kenya'
]
const webTechs = [
'HTML',
'CSS',
'JavaScript',
'React',
'Redux',
'Node',
'MongoDB'
]
```
1. Declare an _empty_ array;
2. Declare an array with more than 5 number of elements
3. Find the length of your array
@ -712,6 +686,31 @@ const webTechs = [
### Exercise: Level 2
1. Create a separate countries.js file and store the countries array in to this file, create a separate file web_techs.js and store the webTechs array in to this file. Access both file in main.js file
```js
const countries = [
'Albania',
'Bolivia',
'Canada',
'Denmark',
'Ethiopia',
'Finland',
'Germany',
'Hungary',
'Ireland',
'Japan',
'Kenya'
]
const webTechs = [
'HTML',
'CSS',
'JavaScript',
'React',
'Redux',
'Node',
'MongoDB'
]
```
1. First remove all the punctuations and change the string to array and count the number of words in the array
The above code stops if 3 found in the iteration process.
The above code stops if 3 is found in the iteration process.
### continue
@ -420,7 +420,7 @@ for(let i = 0; i <= 5; i++){
['Finland','Ireland', 'Iceland']
```
3. In above countries array, check if there is a country or countries end with a substring 'ia'. If there are countries end with, print it as array. If there is no country containing the word 'ai', print 'These are countries ends without ia'.
3. In above countries array, check if there is a country or countries end with a substring 'ia'. If there are countries end with, print it as array. If there is no country containing the word 'ia', print 'These countries do not end with ia'.
```sh
['Albania', 'Bolivia','Ethiopia']
@ -474,7 +474,6 @@ for(let i = 0; i <= 5; i++){
1. Sort the webTechs array and mernStack array
1. Extract all the countries contain the word 'land' from the [countries array](https://github.com/Asabeneh/30DaysOfJavaScript/tree/master/data/countries.js) and print it as array
1. Find the country containing the hightest number of characters in the [countries array](https://github.com/Asabeneh/30DaysOfJavaScript/tree/master/data/countries.js)
1. Extract all the countries contain the word 'land' from the [countries array](https://github.com/Asabeneh/30DaysOfJavaScript/tree/master/data/countries.js) and print it as array
1. Extract all the countries containing only four characters from the [countries array](https://github.com/Asabeneh/30DaysOfJavaScript/tree/master/data/countries.js) and print it as array
1. Extract all the countries containing two or more words from the [countries array](https://github.com/Asabeneh/30DaysOfJavaScript/tree/master/data/countries.js) and print it as array
1. Reverse the [countries array](https://github.com/Asabeneh/30DaysOfJavaScript/tree/master/data/countries.js) and capitalize each country and stored it as an array
So far we have seen many builtin JavaScript functions. In this section, we will focus on custom functions. What is a function? Before we start making functions, lets understand what function is and why we need function?
A function is a reusable block of code or programming statements designed to perform a certain task.
A function is declared by a function key word followed by a name, followed by parentheses (). A parentheses can take a parameter. If a function take a parameter it will be called with argument. A function can also take a default parameter. To store a data to a function, a function has to return certain data types. To get the value we call or invoke a function.
A function is declared with the function key word followed by a name, followed by parentheses (). A parentheses can take a parameter. If a function takes a parameter it will be called with argument. A function can also take a default parameter. To store a data to a function, a function has to return certain data types. To get the value we call or invoke a function.
Function makes code:
- clean and easy to read
@ -74,7 +74,7 @@ functionName() // calling function by its name and with parentheses
### Function without a parameter and return
Function can be declared without a parameter.
Functions can be declared without a parameter.
**Example:**
@ -114,7 +114,7 @@ printFullName() // calling a function
### Function returning value
Function can also return values, if a function does not return values the value of the function is undefined. Let us write the above functions with return. From now on, we return value to a function instead of printing it.
Functions can also return values, if a function does not return values the value of the function is undefined. Let us write the above functions with return. From now on, we return value to a function instead of printing it.
```js
function printFullName (){
@ -147,7 +147,7 @@ In a function we can pass different data types(number, string, boolean, object,
```js
// function with one parameter
function functionName(parm1) {
//code goes her
//code goes here
}
functionName(parm1) // during calling or invoking one argument needed
@ -170,7 +170,7 @@ console.log(square(10))
```js
// function with two parameters
function functionName(parm1, parm2) {
//code goes her
//code goes here
}
functionName(parm1, parm2) // during calling or invoking two arguments needed
// Function without parameter doesn't take input, so lets make a function with parameters
@ -203,7 +203,7 @@ function functionName(parm1, parm2, parm3,...){
functionName(parm1,parm2,parm3,...) // during calling or invoking three arguments needed
// this function takes array as a parameter and sum up the numbers in the array
// this function takes an array as a parameter and sums up the numbers in the array
function sumArrayValues(arr) {
let sum = 0;
for (let i = 0; i <arr.length;i++){
@ -504,7 +504,7 @@ console.log('Weight of an object in Newton: ', weightOfObject(100, 1.62)) // gra
It Will be covered in other section.
🌕 You are a rising star, now you knew function . Now, you are super charged with the power of functions. You have just completed day 7 challenges and you are 7 steps ahead in to your way to greatness. Now do some exercises for your brain and for your muscle.
🌕 You are a rising star, now you know functions. Now, you are super charged with the power of functions. You have just completed day 7 challenges and you are 7 steps ahead in to your way to greatness. Now do some exercises for your brain and for your muscles.
@ -512,7 +512,7 @@ It Will be covered in other section.
### Exercises: Level 1
1. Declare a function _fullName_ and it print out your full name.
1. Declare a function _fullName_ and make it print out your full name.
2. Declare a function _fullName_ and now it takes firstName, lastName as a parameter and it returns your full - name.
3. Declare a function _addNumbers_ and it takes two two parameters and it returns sum.
4. An area of a rectangle is calculated as follows: _area = length x width_. Write a function which calculates _areaOfRectangle_.
@ -521,13 +521,13 @@ It Will be covered in other section.
7. Area of a circle is calculated as follows: _area = π x r x r_. Write a function which calculates _areaOfCircle_
8. Circumference of a circle is calculated as follows: _circumference = 2πr_. Write a function which calculates _circumOfCircle_
9. Density of a substance is calculated as follows:_density= mass/volume_. Write a function which calculates _density_.
10. Speed is calculated by dividing the total distance covered by a moving object divided by the total amount of time taken. Write a function which calculates a speed of a moving object, _speed_.
10. Speed is calculated by dividing the total distance covered by a moving object by the total amount of time taken. Write a function which calculates a speed of a moving object, _speed_.
11. Weight of a substance is calculated as follows: _weight = mass x gravity_. Write a function which calculates _weight_.
12. Temperature in oC can be converted to oF using this formula: _oF = (oC x 9/5) + 32_. Write a function which convert oC to oF _convertCelsiusToFahrenheit_.
12. Temperature in oC can be converted to oF using this formula: _oF = (oC x 9/5) + 32_. Write a function which converts oC to oF _convertCelsiusToFahrenheit_.
13. Body mass index(BMI) is calculated as follows: _bmi = weight in Kg / (height x height) in m2_. Write a function which calculates _bmi_. BMI is used to broadly define different weight groups in adults 20 years old or older.Check if a person is _underweight, normal, overweight_ or _obese_ based the information given below.
- The same groups apply to both men and women.
- _Underweight_: BMI is less than 18.5
- _Underweight_: BMI is less than 18.4
- _Normal weight_: BMI is 18.5 to 24.9
- _Overweight_: BMI is 25 to 29.9
- _Obese_: BMI is 30 or more
@ -601,7 +601,7 @@ It Will be covered in other section.
sum(1, 2, 3, 4) // -> 10
```
1. Writ a function which generates a _randomUserIp_.
1. Write a function which generates a _randomUserIp_.
1. Write a function which generates a _randomMacAddress_
1. Declare a function name _randomHexaNumberGenerator_. When this function is called it generates a random hexadecimal number. The function return the hexadecimal number.
@ -659,12 +659,12 @@ It Will be covered in other section.
```
1. Call your function _shuffleArray_, it takes an array as a parameter and it returns a shuffled array
1. Call your function _factorial_, it takes a whole number as a parameter and it return a factorial of the number
1. Call your function _factorial_, it takes a whole number as a parameter and it returns a factorial of the number
1. Call your function _isEmpty_, it takes a parameter and it checks if it is empty or not
1. Call your function _sum_, it takes any number of arguments and it returns the sum.
1. Write a function called _sumOfArrayItems_, it takes an array parameter and return the sum of all the items. Check if all the array items are number types. If not give return reasonable feedback.
1. Write a function called _average_, it takes an array parameter and returns the average of the items. Check if all the array items are number types. If not give return reasonable feedback.
1. Write a function called _modifyArray_ takes array as parameter and modifies the fifth item of the array and return the array. If the array length is less than five it return 'item not found'.
1. Write a function called _sumOfArrayItems_, it takes an array parameter and returns the sum of all the items. Check if all the array items are number types. If not give return reasonable feedback.
1. Write a function called _average_, it takes an array parameter and returns the average of the items. Check if all the array items are number types. If not return reasonable feedback.
1. Write a function called _modifyArray_ takes an array as parameter and modifies the fifth item of the array and returns the array. If the array length is less than five it returns 'item not found'.
@ -693,15 +693,15 @@ It Will be covered in other section.
1. Write a function called _isPrime_, which checks if a number is prime number.
1. Write a functions which checks if all items are unique in the array.
1. Write a function which checks if all the items of the array are the same data type.
1. JavaScript variable name does not support special characters or symbols except \$ or \_. Write a function **isValidVariable** which check if a variable is valid or invalid variable.
1. JavaScript variable names do not support special characters or symbols except \$ or \_. Write a function **isValidVariable** which checks if a variable name is valid or invalid.
1. Write a function which returns array of seven random numbers in a range of 0-9. All the numbers must be unique.
```js
sevenRandomNumbers()
[(1, 4, 5, 7, 9, 8, 0)]
[1, 4, 5, 7, 9, 8, 0]
```
1. Write a function called reverseCountries, it takes countries array and first it copy the array and returns the reverse of the original array
1. Write a function called reverseCountries, it takes the countries array and first it copy the array and returns the reverse of the original array
Programming languages are similar to human languages. English or many other language uses words, phrases, sentences, compound sentences and other more to convey a meaningful message. The English meaning of syntax is _the arrangement of words and phrases to create well-formed sentences in a language_. The technical definition of syntax is the structure of statements in a computer language. Programming languages have syntax. JavaScript is a programming language and like other programming languages it has its own syntax. If we do not write a syntax that JavaScript understands, it will raise different types of errors. We will explore different kinds of JavaScript errors later. For now, let us see syntax errors.
Programming languages are similar to human languages. English and many other languages use words, phrases, sentences, compound sentences and more to convey meaningful messages. The English meaning of syntax is _the arrangement of words and phrases to create well-formed sentences in a language_. The technical definition of syntax is the structure of statements in a computer language. Programming languages have syntax. JavaScript is a programming language and like other programming languages it has its own syntax. If we do not write a syntax that JavaScript understands, it will raise different types of errors. We will explore different kinds of JavaScript errors later. For now, let us see syntax errors.
ThomSullivan
3 years ago