JavaScript Fundamentals: Loop Types

In this post, we will quickly run through 7 different ways of performing Loops in JavaScript by looking at examples.

Looping

for loop

for (initialExpression; condition; updateExpression) {
  // for loop body
}

const cars = ['Toyota', 'Nissan', 'Mitsubishi'];

for (let i = 0; i < cars.length; i++) {
  console.log(cars[i]);
}

while loop

while (condition) {
  // while loop body
}

const cars = ['Toyota', 'Nissan', 'Mitsubishi'];

let i = 0;

while (i < cars.length) {
  console.log(cars[i]);
  i++;
}

do-while loop

do {
  // do-while loop body
} while (conditon);

const cars = ['Toyota', 'Nissan', 'Mitsubishi'];

let i = 0;

do {
  console.log(cars[i]);
  i++;
} while (i < cars.length);

forEach loop

array.forEach(function(currentValue, index, arr));

const cars = ['Toyota', 'Nissan', 'Mitsubishi'];

cars.forEach((element) => {
  console.log(element);
});

map loop

array.map(function(currentValue, index, arr), thisValue);

const cars = ['Toyota', 'Nissan', 'Mitsubishi'];

const newCars = cars.map((e) => {
  return e.toUpperCase();
});

for-of loop

for (element of iterable) {
  // for-of loop body
}

const cars = ['Toyota', 'Nissan', 'Mitsubishi'];

for (let element of cars) {
  console.log(element);
}

for-in loop

for (key in object) {
  // for-in loop body
}

const cars = { 1: 'Toyota', 2: 'Nissan', 3: 'Mitsubishi' };

for (let key in cars) {
  console.log(cars[key]);
}