JavaScript Array Object

January 17, 2020

JavaScript Array Object

The JavaScript Array class is a global object that is used in the construction of arrays. Arrays are list-like objects whose prototype has methods to perform traversal and mutation operations. Neither the length of a JavaScript array nor the types of its elements are fixed. Since an array's length can change at any time, and data can be stored at non-contiguous locations in the array

The shift() method removes the first element from an array and returns that removed element. This method changes the length of the array.

const array1 = [1, 2, 3];
const firstElement = array1.shift();
// expected output: Array [2, 3]
// expected output: 1

The unshift() method adds one or more elements to the beginning of an array and returns the new length of the array.

const array1 = [1, 2, 3];
console.log(array1.unshift(4, 5));
// expected output: 5
// expected output: Array [4, 5, 1, 2, 3]

The concat() method is used to merge two or more arrays. This method does not change the existing arrays, but instead returns a new array.

const array1 = ['a', 'b', 'c'];
const array2 = ['d', 'e', 'f'];
const array3 = array1.concat(array2);
// expected output: Array ["a", "b", "c", "d", "e", "f"]

const num1 = [1, 2, 3];
const num2 = [4, 5, 6];
const num3 = [7, 8, 9];
const numbers = num1.concat(num2, num3);
// results in [1, 2, 3, 4, 5, 6, 7, 8, 9]

The slice() method returns a shallow copy of a portion of an array into a new array object selected from begin to end (end not included) where begin and end represent the index of items in that array. The original array will not be modified.

const animals = ['ant', 'bison', 'camel', 'duck', 'elephant'];
// expected output: Array ["camel", "duck", "elephant"]
console.log(animals.slice(2, 4));
// expected output: Array ["camel", "duck"]
console.log(animals.slice(1, 5));
// expected output: Array ["bison", "camel", "duck", "elephant"]