Page 105 - JavaScript

var arr1 = ["a","b"];
var arr2 = ["e", "f"];

var arrConc = arr1.concat("c", "d", arr2);

Results in a new Array:

["a", "b", "c", "d", "e", "f"]

Append / Prepend items to Array

Unshift

Use .unshift to add one or more items in the beginning of an array.

For example:

var array = [3, 4, 5, 6];
array.unshift(1, 2);

array results in:

[1, 2, 3, 4, 5, 6]

Push

Further .push is used to add items after the last currently existent item.

For example:

var array = [1, 2, 3];
array.push(4, 5, 6);

array results in:

[1, 2, 3, 4, 5, 6]

Both methods return the new array length.

Object keys and values to array

var object = {
key1: 10,
key2: 3,
key3: 40,
key4: 20
};

https://riptutorial.com/ 62