javascript for each element add 1 element off another array code example

Example 1: javascript push all elements of array to another array

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

Example 2: javascript add 1 to each element in array

var numberarr2 = numberarr.map( function(value) { 
    return value - 1; 
} );