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30-Days-Of-JavaScript
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@ -1107,8 +1107,8 @@ console.log(string.repeat(10)) // lovelovelovelovelovelovelovelovelovelove
15. What is the character code of J in '30 Days Of JavaScript' string using __charCodeAt()__ 15. What is the character code of J in '30 Days Of JavaScript' string using __charCodeAt()__
16. Use __indexOf__ to determine the position of the first occurrence of a in 30 Days Of JavaScript 16. Use __indexOf__ to determine the position of the first occurrence of a in 30 Days Of JavaScript
17. Use __lastIndexOf__ to determine the position of the last occurrence of a in 30 Days Of JavaScript. 17. Use __lastIndexOf__ to determine the position of the last occurrence of a in 30 Days Of JavaScript.
18. Use __indexOf__ 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'__ 18. 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'__
19. Use __lastIndexOf__ 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'__ 19. 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'__
20. 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 __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'__
21. Use __trim()__ to remove if there is trailing whitespace at the beginning and the end of a string.E.g ' 30 Days Of JavaScript '. 21. Use __trim()__ to remove if there is trailing whitespace at the beginning and the end of a string.E.g ' 30 Days Of JavaScript '.
22. Use __startsWith()__ method with the string *30 Days Of JavaScript* make the result true 22. Use __startsWith()__ method with the string *30 Days Of JavaScript* make the result true
@ -1185,263 +1185,4 @@ Arithmetic operators are mathematical operators.
```js ```js
let numOne = 4; let numOne = 4;
let numTwo = 3; let numTwo = 3;
let sum = numOne + numTwo; let sum
let diff = numOne - numTwo;
let mult = numOne * numTwo;
let div = numOne / numTwo;
let remainder = numOne % numTwo;
let powerOf = numOne ** numTwo
console.log(sum, diff, mult, div, remainder, powerOf); // ->7,1,12,1.33,1, 64
let PI = 3.14;
let radius = 100; // length in meter
const gravity = 9.81; // in m/s2
let mass = 72; // in Kilogram
const boilingPoint = 100; // temperature in oC, boiling point of water
const bodyTemp = 37; // body temperature in oC
//Let us calculate area of a circle
const areaOfCircle = PI * radius * radius;
console.log(areaOfCircle); // -> 314 m
// Let us calculate weight of an object
const weight = mass * gravity;
console.log(weight); // -> 706.32 N(Newton)
//Concatenating string with numbers using string interpolation
/*
The boiling point of water is 100 oC.
Human body temperature is 37 oC.
The gravity of earth is 9.81 m/s2.
*/
console.log(
`The boiling point of water is ${boilingPoint} oC.\nHuman body temperature is ${bodyTemp} oC.\nThe gravity of earth is ${gravity} m / s2.`
);
```
### Comparison Operators
In programming we compare values, we use comparison operators to compare two values. We check if a value is greater or less or equal to other value.
![Comparison Operators](./images/comparison_operators.png)
**Example: Comparison Operators**
```js
console.log(3 > 2) // true, because 3 is greater than 2
console.log(3 >= 2) // true, because 3 is greater than 2
console.log(3 < 2) // false, because 3 is greater than 2
console.log(2 < 3) // true, because 2 is less than 3
console.log(2 <= 3) // true, because 2 is less than 3
console.log(3 == 2) // false, because 3 is not equal to 2
console.log(3 != 2) // true, because 3 is not equal to 2
console.log(3 == '3') // true, compare only value
console.log(3 === '3') // false, compare both value and data type
console.log(3 !== '3') // true, compare both value and data type
console.log(3 !== '3') // true, compare both value and data type
console.log(3 != 3) // false, compare only value
console.log(3 !== 3) // false, compare both value and data type
console.log('mango'.length == 'avocado'.length) // false
console.log('mango'.length != 'avocado'.length) // true
console.log('mango'.length < 'avocado'.length) // true
console.log('milk'.length != 'meat'.length) // false
console.log('milk'.length == 'meat'.length) // true
console.log('tomato'.length == 'potato'.length) // true
console.log('python'.length > 'dragon'.length) // false
```
### Logical Operators
The following symbols are the common logical operators:
&&(ampersand) , ||(pipe) and !(negation).
&& gets true only if the two operands are true.
|| gets true either of the operand is true.
! negates true to false, false to true.
```js
//&& ampersand example
const check = 4 > 3 && 10 > 5; // true and true -> true
const check = 4 > 3 && 10 < 5; // true and false -> false
const check = 4 < 3 && 10 < 5; // false and false -> false
//|| pipe or, example
const check = 4 > 3 || 10 > 5; // true and true -> true
const check = 4 > 3 || 10 < 5; // true and false -> true
const check = 4 < 3 || 10 < 5; // false and false -> false
//! Negation examples
let check = 4 > 3; // -> true
let check = !(4 > 3); // -> false
let isLightOn = true;
let isLightOff = !isLightOn; // -> false
let isMarried = !false; // -> true
```
### Increment Operator
In JavaScrip we use the increment operator to increase a value stored in a variable. The increment could be pre or post increment. Let us see each of them:
1. Pre-increment
```js
let count = 0
console.log(++count) // 1
console.log(count) // 1
```
2. Post-increment
```js
let count = 0
console.log(count++) // 0
console.log(count) // 1
```
We use most of the time post-increment. At leas you should remember how to use post-increment operator.
### Decrement Operator
In JavaScrip we use the decrement operator to decrease a value stored in a variable. The decrement could be pre or post decrement. Let us see each of them:
1. Pre-decrement
```js
let count = 0
console.log(--count) // -1
console.log(count) // -1
```
2. Post-decrement
```js
let count = 0
console.log(count--) // 0
console.log(count) // -1
```
### Operator Precendence
I would like to recommend you to read about operator precendence from this [link](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence)
## Date Object
Time is an important thing. We like to know the time a certain activity or event. In JavaScript current time and date is created using JavaScript Date Object. The object we create using Date object provides many methods to work with date and time.The methods we use to get date and time information from a date object values are started with a word _get_ because it provide the information.
_getFullYear(), getMonths(), getDate(), getDay(), getHours(), getMinutes, getSeconds(), getMilliseconds(), getTime(), getDay()_
![Date time Object](images/date_time_object.png)
### Creating a time object
Once we create time object. The time object will provide information about time. Let us create a time object
```js
const now = new Date () //
console.log(now) // Sat Jan 04 2020 00:56:41 GMT+0200 (Eastern European Standard Time)
```
We have created a time object and we can access any date time information from the object using the get methods we have mentioned on the table.
### Getting full year
Let's extract or get the full from a time object.
```js
const now = new Date () //
console.log(now.getFullYear()) // 2020
```
### Getting month
Let's extract or get the month from a time object.
```js
const now = new Date () //
console.log(now.getMonth()) // 0, because the month is January, month(0-11)
```
### Getting date
Let's extract or get the date of the month from a time object.
```js
const now = new Date () //
console.log(now.getMonth()) // 0, because the month is January, month(0-11)
```
### Getting hours
Let's extract or get the hours from a time object.
```js
const now = new Date () //
console.log(now.getHours()) // 0, because the time is 00:56:41
```
### Getting minutes
Let's extract or get the minutes from a time object.
```js
const now = new Date () //
console.log(now.getMinutes()) // 56, because the time is 00:56:41
```
### Getting seconds
Let's extract or get the minutes from a time object.
```js
const now = new Date () //
console.log(now.getMinutes()) // 56, because the time is 00:56:41
```
### Getting time
This method give time in milliseconds starting from January 1, 1970. It is also know as Unix time. We can get the unix time in two ways:
1. Using *getTime()*
```js
const now = new Date () //
console.log(now.getTime()) // 1578092201341, this is the number of seconds passed from January 1, 1970 to January 4, 2020 00:56:41
```
2. Using *Date.now()*
```js
const allSeconds = Date.now () //
console.log(allSeconds) // 1578092201341, this is the number of seconds passed from January 1, 1970 to January 4, 2020 00:56:41
const timeInSeconds = new Date ().getTime()
console.log(allSeconds == timeInSeconds) // true
```
Let us format these values to a human readable time format.
**Example:**
```js
const now = new Date ();
const year = now.getFullYear(); // return year
const month = now.getMonth() + 1; // return month(0 - 11)
const date = now.getDate(); // return date (1 - 31)
const hours = now.getHours(); // return number (0 - 23)
const minutes = now.getMinutes();// return number (0 -59)
console.log(`${date}/${month}/${year} ${hours}:${minutes}`) // 4/1/2020 0:56
```
# 💻 Day 3: Exercises
## 1. Exercises: Data types Part
1. Declare firstName, lastName, country, city, age, isMarried, year variable and assign value to it
1. The JavaScript typeof operator uses to check different data types. Check the data type of each variables from question number 1.
## 2. Exercises: Arithmetic Operators Part
JavaScript arithmetic operators are addition(+), subtraction(-), multiplication(*), division(/), modulus(%), exponential(**), increment(++) and decrement(--).
```js
let operandOne = 4;
let operandTwo = 3;
```
Using the above operands apply different JavaScript arithmetic operations.
## 3. Exercises: Booleans Part
Boolean value is either true or false.
1. Write three JavaScript statement which provide truthy value.
1. Write three JavaScript statement which provide falsy value.
## 4. Exercises: Comparison Operators
Figure out the result of the following comparison expression first without using console.log(). After you decide the result confirm it using console.log()
1. 4 > 3
1. 4 >= 3
1. 4 < 3
1. 4 <= 3
1. 4 == 4
1. 4 === 4
1. 4 != 4
1. 4 !== 4
1. 4 != '4'
1. 4 == '4'
1. 4 === '4'
## 5. Exercises: Logical Operators
Figure out the result of the following expressions first without using console.log(). After you decide the result confirm it by using console.log()
1. 4 > 3 && 10 < 12
1. 4 > 3 && 10 > 12
1. 4 > 3 || 10 < 12
1. 4 > 3 || 10 > 12
1. !(4 > 3)
1. !(4 < 3)
1. !(false)
1. !(4 > 3 && 10 < 12)
1. !(4 > 3 && 10 > 12)
1. !(4 === '4')
## 6. Exercises: Date time Object
1. What is the year today?
1. What is the month today?
1. What is the date today?
1. What is the day today?
1. What is the hours now?
1. What is the minutes now?
1. Find out the numbers of seconds elapsed from January 1, 1970 to now.
1. Create a human readable time format
1. YYY-MM-DD HH:mm:ss
2. DD-MM-YYYY HH:mm:ss
3. DD/MM/YYY HH:mm:ss

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