Introduction

Hey folks, I hope that you must have read my Day 5 Article on #30DaysOfJs. In case, if you haven't then make sure you give it a read by clicking here.

Loops

In the programming world, whenever we need to perform repetitive tasks, such as printing 0 to 100 numbers in the console, we use different kinds of loops. Some of the most commonly used loops used in JavaScript and other programming languages are:

• for Loop:

Syntax:

// For Loop Structure
for(initialization, condition, increment/decrement){
  // Code
}

For Example 1:

for(let i = 0; i <= 5; i++){
  console.log(i);
}

// Output:
// 0 1 2 3 4 5

For Example 2:

for(let i = 0; i <= 5; i++){
  console.log(`${i} * ${i} = ${i * i}`);
}

// Output:
// 0 * 0 = 0
// 1 * 1 = 1
// 2 * 2 = 4
// 3 * 3 = 9
// 4 * 4 = 16
// 5 * 5 = 25

For Example 3:

const countries = ['India', 'America', 'Canada', 'Norway', 'Iceland']
const newArr = []
for(let i = 0; i < countries.length; i++){
  newArr.push(countries[i].toUpperCase())
}

// Output:
// ["INDIA", "AMERICA", "CANADA", "NORWAY", "ICELAND"]

• while Loop: In this Loop the variable i iterates from 0 to 5 and as per its logic, all the numbers get printed in the console.

Syntax:

let i = 0
while (i <= 5) {
  console.log(i);
  i++
}

// Output:
// 0 1 2 3 4 5

• do while Loop:

Syntax:

let i = 0
do {
  console.log(i);
  i++
} while (i <= 5)

// Output:
// 0 1 2 3 4 5

• for of Loop: This method is quite easy to use when one wants to iterate through arrays and is not interested in the index of each element in the array.

Syntax:

for (const element of arr) {
  // Code
}

For Example:

const numbers = [1, 2, 3, 4, 5]

for (const num of numbers) {
  console.log(num);
}

// Output:
// 1 2 3 4 5

for (const num of numbers) {
  console.log(num * num)
}

// Output:
// 1 4 9 16 25

// Adding all the numbers in the array
let sum = 0
for (const num of numbers) {
  sum = sum + num  
}
console.log(sum); 

// Output:
// 15

const webTechs = ['MongoDB', 'Express', 'React', 'Node'];

for (const tech of webTechs) {
  console.log(tech.toUpperCase())
}

// Output:
// MONGODB EXPRESS REACT NODE

• break: break statements are used to interrupt a process in any given loop.

For Example:

for(let i = 0; i <= 5; i++){
  if(i == 3){
    break
  }
  console.log(i)
}

// Output:
// 0 1 2

In the above example, when the loop comes at i = 3, the break statement executes and the iteration process stops.

• continue: continue statement is used whenever we need to skip certain iterations.

For Example:

for(let i = 0; i <= 5; i++){
  if(i == 3){
    continue
  }
  console.log(i);
}

// Output:
// 0 1 2 4 5

In the above example, when i comes to position 3 it skips this number and moves forward in the lo.

I hope that you must have found this article quite helpful. If yes, then do give a read to some of my other articles!

Who knows you might become a great programmer 🤔!