Double the occurence of character in Javascript

Question

Input String : abcd

Output String : aabbccdd

How to achieve this using Javascript if 'a' 'b' 'c' 'd' are an elements of an array ..

Answer 1

Simple regex solution:

"abcd".replace(/[\S\s]/g, "$&$&");

Array solution:

"abcd".split("").map(function(x){return x+x}).join("");

For a more generic solution of the string repetition (in the array solution), have a look at Repeat String - Javascript.

Or do it the minimalistic way with loops:

var input = "abcd";
var output = "";
for (var i=0; i<input.length; i++) {
    var chr = input.charAt(i);
    for (var j=0; j<2; j++)
        output += chr;
}

Answer 2

Try this...

var a = "abcd";
var b = "";
for(var i = 0; i < a.length; i++)
    b += a.charAt(i) + a.charAt(i);