phpjs/workbench/bc/bcsqrt.js

php.js offers community built php functions in javascript

function bcsqrt(operand, scale) {
  // http://kevin.vanzonneveld.net
  // +   original by: Robin Speekenbrink (http://www.kingsquare.nl/))

  var out = Math.sqrt(operand);
  if (typeof precision !== 'undefined') {
    out = Math.round(Math.round(out * Math.pow(10, scale + 1)) / Math.pow(10, 1)) / Math.pow(10, scale);
  }
  return out;
}