Iterate Through an Array with a For Loop code example

Example 1: javascript loop through array

var data = [1, 2, 3, 4, 5, 6];

// traditional for loop
for(let i=0; i<=data.length; i++) {
  console.log(data[i])  // 1 2 3 4 5 6
}

// using for...of
for(let i of data) {
	console.log(i) // 1 2 3 4 5 6
}

// using for...in
for(let i in data) {
  	console.log(i) // Prints indices for array elements
	console.log(data[i]) // 1 2 3 4 5 6
}

// using forEach
data.forEach((i) => {
  console.log(i) // 1 2 3 4 5 6
})
// NOTE ->  forEach method is about 95% slower than the traditional for loop

// using map
data.map((i) => {
  console.log(i) // 1 2 3 4 5 6
})

Example 2: how to loop through array of numbers in javascript

let numbers = [1,2,3,4,5];
let numbersLength = numbers.length;
for ( let i = 0; i < numbersLength; i++) {
    console.log (numbers[i]);
}

Example 3: iterate through an array

var arr = [1,2,3,4,5,6,7,8];

// Uses the usual "for" loop to iterate
for(var i= 0, l = arr.length; i< l; i++){
	console.log(arr[i]);
}

console.log("========================");

//Uses forEach to iterate
arr.forEach(function(item,index){
	console.log(item);
});

Example 4: Iterate Through an Array with a For Loop

var arr = [10, 9, 8, 7, 6];
for (var i = 0; i < arr.length; i++) {
   console.log(arr[i]);
}

Example 5: Iterate Through an Array with a For Loop

var arr = [10, 9, 8, 7, 6];
for (var i = 0; i < arr.length; i++) {
   console.log(arr[i]);
}

Example 6: javascript loop through array

// looping through an array in javascript using our own myEach function

// Write an `Array.prototype.myEach(callback)` method that invokes a callback
// for every element in an array and returns undefined.
Array.prototype.myEach = function(callback) {
    for (let i = 0 ; i < this.length ; i ++) {
        callback(this[i]);
    }
}

let array = ['Item 1', 'Item 2', 'Item 3', 'Item 4'];

array.myEach(function (element) {
	console.log(element); // this will print each element in the array
    // Code to do something to each element in the array
});