how to insert item to array + javascript code example

Example 1: add item to array javascript

const arr1 = [1,2,3]
const newValue = 4
const newData = [...arr1, obj] // [1,2,3,4]

Example 2: js add array items to array

var arrayA = [1, 2];
var arrayB = [3, 4];
var newArray = arrayA.concat(arrayB);