#functions

closures || map method || arguments || map method how internally works

var map = function(arr, fn) { let n=arr.length; let arr2=[]; for(let i=0;i<n;i++){ //here we can call this function with 0 || 1 || 2 no of arguments arr2.push(fn(arr[i],i)); } return arr2; }; function arguments behavior ...