phpjs/functions/strings/stristr.js

php.js offers community built php functions in javascript

function stristr(haystack, needle, bool) {
  // From: http://phpjs.org/functions
  // +   original by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // +   bugfxied by: Onno Marsman
  // *     example 1: stristr('Kevin van Zonneveld', 'Van');
  // *     returns 1: 'van Zonneveld'
  // *     example 2: stristr('Kevin van Zonneveld', 'VAN', true);
  // *     returns 2: 'Kevin '
  var pos = 0;

  haystack += '';
  pos = haystack.toLowerCase().indexOf((needle + '').toLowerCase());
  if (pos == -1) {
    return false;
  } else {
    if (bool) {
      return haystack.substr(0, pos);
    } else {
      return haystack.slice(pos);
    }
  }
}