1. Home
  2. Javascript
  3. JavaScript Array Iteration

 JavaScript Array Iteration JAVASCRIPT

JavaScript Array Iteration  


JavaScript Array Iteration

JavaScript Array Iteration Methods

Array iteration methods operate on every array item.

Array.forEach()

The forEach() method calls a function (a callback function) once for each array element.

Example

var txt = "";
var numbers = [45, 4, 9, 16, 25];
numbers.forEach(myFunction);

function myFunction(value, index, array) {
  txt = txt + value + "<br>";
}

Array.map()

The map() method creates a new array by performing a function on each array element.

The map() method does not execute the function for array elements without values.

The map() method does not change the original array.

Example

var numbers1 = [45, 4, 9, 16, 25];
var numbers2 = numbers1.map(myFunction);

function myFunction(value, index, array) {
  return value * 2;
}

Array.filter()

The filter() method creates a new array with array elements that pass a test.

Example

var numbers = [45, 4, 9, 16, 25];
var over18 = numbers.filter(myFunction);

function myFunction(value, index, array) {
  return value > 18;
}

Array.reduce()

The reduce() method runs a function on each array element to produce (reduce it to) a single value.

The reduce() method works from left-to-right in the array. See also reduceRight().

The reduce() method does not reduce the original array.

Example

var numbers1 = [45, 4, 9, 16, 25];
var sum = numbers1.reduce(myFunction);

function myFunction(total, value, index, array) {
  return total + value;
}

Array.reduceRight()

The reduceRight() method runs a function on each array element to produce (reduce it to) a single value.

The reduceRight() works from right-to-left in the array. See also reduce().

The reduceRight() method does not reduce the original array.

Example

var numbers1 = [45, 4, 9, 16, 25];
var sum = numbers1.reduceRight(myFunction);

function myFunction(total, value, index, array) {
  return total + value;
}

Array.every()

The every() method checks if all array values pass a test.

Example

var numbers = [45, 4, 9, 16, 25];
var allOver18 = numbers.every(myFunction);

function myFunction(value, index, array) {
  return value > 18;
}

Array.some()

The some() method check if some array values pass a test.

Example

var numbers = [45, 4, 9, 16, 25];
var someOver18 = numbers.some(myFunction);

function myFunction(value, index, array) {
  return value > 18;
}

Array.indexOf()

The indexOf() method searches an array for an element value and returns its position.

Example

var fruits = ["Apple", "Orange", "Apple", "Mango"];
var a = fruits.indexOf("Apple");

Array.lastIndexOf()

Array.lastIndexOf() is the same as Array.indexOf(), but returns the position of the last occurrence of the specified element.

Example

var fruits = ["Apple", "Orange", "Apple", "Mango"];
var a = fruits.lastIndexOf("Apple");

Array.find()

The find() method returns the value of the first array element that passes a test function.

Example

var numbers = [4, 9, 16, 25, 29];
var first = numbers.find(myFunction);

function myFunction(value, index, array) {
  return value > 18;
}

Array.findIndex()

The findIndex() method returns the index of the first array element that passes a test function.

Example

var numbers = [4, 9, 16, 25, 29];
var first = numbers.findIndex(myFunction);

function myFunction(value, index, array) {
  return value > 18;
}

Array.findIndex()

The findIndex() method returns the index of the first array element that passes a test function.

Example

var numbers = [4, 9, 16, 25, 29];
var first = numbers.findIndex(myFunction);

function myFunction(value, index, array) {
  return value > 18;
}

Download free E-book of JAVASCRIPT

#askProgrammers
Learn Programming for Free

Join Programmers Community on Telegram

Talk with Experienced Programmers

Just drop a message, we will solve your queries