phpjs/functions/strings/strcasecmp.js

php.js offers community built php functions in javascript

function strcasecmp(f_string1, f_string2) {
  //  discuss at: http://phpjs.org/functions/strcasecmp/
  // original by: Martijn Wieringa
  // bugfixed by: Onno Marsman
  //   example 1: strcasecmp('Hello', 'hello');
  //   returns 1: 0

  var string1 = (f_string1 + '')
    .toLowerCase();
  var string2 = (f_string2 + '')
    .toLowerCase();

  if (string1 > string2) {
    return 1;
  } else if (string1 == string2) {
    return 0;
  }

  return -1;
}