Loops in javascript

for loop:

Single for loop: Below is the syntax of a for loop with the example of skipping the even numbers and printing the odd numbers between 1 to 10.

 for (let i = 0; i <=10; i++) {
     const element = i;
     if (element%2==0) {
         continue
     }
     console.log(element);
 }

Nested for loop: Below is an example of printing the table of 1 to 5 using the nested for loop.


 for (let i = 1; i <= 5; i++) {
     console.log(`inner loop value: ${i}`);
     for (let j = 1; j <=10 ; j++) {
         console.log(i +'*'+ j +'='+ i*j);
     }

 }

For loop on array: Below is an example of accessing all the elements of an array using the for loop.

 const myArray = ['Superman','Batman','Flash']
 for (let index = 0; index < myArray.length; index++) {
     const element = myArray[index];
     console.log(element);
 }
 /*Output: Superman
 Batman
 Flash */

While loop: Below is the syntax for the while loop with an example of printing the even numbers between 0 to 10.
```
 let index = 0
 while (index<=10) {
 console.log(`value of index is ${index}`)
 index+=2;   
 }
```
Do-while loop: The do-while loop is similar to the while loop only difference is do-while loop executes at least once as the condition is checked at the end. Below is an example of do-while loop.
```
 let score=11
 do {
     console.log(`score is ${score}`);
     score++
 } while (score <=10); //do while atleast executes 1 time
```

Array loops: In Javascript, there are some inbuilt loops, particularly for arrays.

For of loop: The demonstration of for of loop on arrays, strings, and maps is as shown below. For this loop, we don't need to give start value, end value, and increment.

 //1. For of loop: 
 //example for array
 const superheroes = ['batman', 'superman','flash']
 for (const heroes of superheroes) {
     console.log(heroes);
 }
 /* Output:
 batman
 superman
 flash
 */

 //example for string
 const greetings = "hello world!"
 for (const greet of greetings) {
     console.log(`each character is ${greet}`);
 }
 /* Output:
 each character is h
 each character is e
 each character is l
 each character is l
 each character is o
 each character is  
 each character is w
 each character is o
 each character is r
 each character is l
 each character is d
 each character is !
 */

 //example for maps
 const maps = new Map()
 maps.set('IN', 'india')
 maps.set('USA', 'united states of america')
 maps.set('FR', 'france')
 maps.set('IN', 'india')  //maps allows unique entries order remains same 

 for (const [key,value] of maps) {
     console.log(key, ':', value);
 }
 /* Output:
 IN : india
 USA : united states of america
 FR : france
 */

For each loop: The demonstration of for-each loop on arrays and objects is as shown below. For this loop, we don't need to give start value, end value, and increment.

 const coding = ["js","ruby","java","python","cpp"]
 coding.forEach( function (item)  {
     console.log(item);
 } )
 /* 
 Output:
 js
 ruby
 java
 python
 cpp
 */

 //accessing object properties [object values]from an array using forEach
 const myCoding = [
     {
         languageName:"javascript",
         languageFileName: "js"
     },
     {
         languageName:"java",
         languageFileName: "java"
     },
     {
         languageName:"python",
         languageFileName: "py"
     },
 ]

 myCoding.forEach( (item) => {
     console.log(item.languageName);
 } )
 /* 
 Output:
 javascript
 java
 python
 */

For in loop: The demonstration of for in loop on arrays, ans objects is as shown below. For this loop, we don't need to give start value, end value, and increment.

 const myObject = {
     'game1': 'NFS',
     'game2': 'Spiderman',
     'game3': "GTA5",
     "game4": "COD warzone"
 }

 for (const key in myObject) {
     console.log(`${key} : ${myObject[key]} game is available to play`)
 }
 /* Output: 
 game1 : NFS game is available to play
 game2 : Spiderman game is available to play
 game3 : GTA5 game is available to play
 game4 : COD warzone game is available to play
 */

 const programming = ["js","ruby","java","cpp","python"]

 for (const key in programming) {
    console.log(programming[key]);
 }
 /* Output: 
 js
 ruby
 java
 cpp
 python
 */