how to map through in an array code example

Example 1: use map to loop through an array

let squares = [1,2,3,4].map(function (val) {  
    return val * val;  
}); 
// squares will be equal to [1, 4, 9, 16]

Example 2: mapping through an array

var numbers = [4, 9, 16, 25];
var x = numbers.map(Math.sqrt)

  document.getElementById("demo").innerHTML = x;