Is there a JavaScript function that can pad a string to get to a determined length?

Question

I am in need of a JavaScript function which can take a value and pad it to a given length (I need spaces, but anything would do). I found this:

Code:

Answer 1

A faster method

If you are doing this repeatedly, for example to pad values in an array, and performance is a factor, the following approach can give you nearly a 100x advantage in speed (jsPerf) over other solution that are currently discussed on the inter webs. The basic idea is that you are providing the pad function with a fully padded empty string to use as a buffer. The pad function just appends to string to be added to this pre-padded string (one string concat) and then slices or trims the result to the desired length.

function pad(pad, str, padLeft) {
  if (typeof str === 'undefined') 
    return pad;
  if (padLeft) {
    return (pad + str).slice(-pad.length);
  } else {
    return (str + pad).substring(0, pad.length);
  }
}

For example, to zero pad a number to a length of 10 digits,

pad('0000000000',123,true);

To pad a string with whitespace, so the entire string is 255 characters,

var padding = Array(256).join(' '), // make a string of 255 spaces
pad(padding,123,true);

Performance Test

See the jsPerf test here.

And this is faster than ES6 string.repeat by 2x as well, as shown by the revised JsPerf here