phpjs/functions/math/sqrt.js

php.js offers community built php functions in javascript

function sqrt(arg) {
  // From: http://phpjs.org/functions
  // +   original by: Onno Marsman
  // *     example 1: sqrt(8723321.4);
  // *     returns 1: 2953.5269424875746
  return Math.sqrt(arg);
}