Curriculum

JavaScript Basic

JSHome

0/216

JS Versions

0/36

JS Objects

0/15

JS Funtions

0/22

JS Classes

0/3

JS Async

0/10

JS HTML DOM

0/25

JS Browser BOM

0/17

JS Web APIs

0/7

JS AJAX

0/11

JS JSON

0/16

JS vs jQuery

0/4

JS Graphics

0/7

Text lesson

Array.isArray()

The isArray() method determines if an object is an array.

Example

function myFunction() {
var fruits = [“Banana”, “Orange”, “Apple”, “Mango”];
var x = document.getElementById(“demo”);
x.innerHTML = Array.isArray(fruits);
}

Array forEach()

The forEach() method executes a function once for each element in an array.

Example

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

function myFunction(value) {
txt = txt + value + “<br>”;
}

Array map()

This example multiplies each value in the array by 2:

Example

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

function myFunction(value) {
return value * 2;
}

Array filter()

This example creates a new array containing elements with values greater than 18:

Example

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

function myFunction(value) {
return value > 18;
}

Array reduce()

This example calculates the sum of all the numbers in an array:

Example

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

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

Array reduceRight()

This example also computes the sum of all the numbers in an array:

Example

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

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

Array every()

This example checks whether all values are greater than 18:

Example

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

function myFunction(value) {
return value > 18;
}

Array some()

This example checks if any values are greater than 18:

Example

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

function myFunction(value) {
return value > 18;
}