phpjs/functions/array/key.js

php.js offers community built php functions in javascript

function key(arr) {
  //  discuss at: http://phpjs.org/functions/key/
  // original by: Brett Zamir (http://brett-zamir.me)
  //    input by: Riddler (http://www.frontierwebdev.com/)
  // bugfixed by: Brett Zamir (http://brett-zamir.me)
  //        note: Uses global: php_js to store the array pointer
  //   example 1: array = {fruit1: 'apple', 'fruit2': 'orange'}
  //   example 1: key(array);
  //   returns 1: 'fruit1'

  this.php_js = this.php_js || {};
  this.php_js.pointers = this.php_js.pointers || [];
  var indexOf = function(value) {
    for (var i = 0, length = this.length; i < length; i++) {
      if (this[i] === value) {
        return i;
      }
    }
    return -1;
  };
  // END REDUNDANT
  var pointers = this.php_js.pointers;
  if (!pointers.indexOf) {
    pointers.indexOf = indexOf;
  }

  if (pointers.indexOf(arr) === -1) {
    pointers.push(arr, 0);
  }
  var cursor = pointers[pointers.indexOf(arr) + 1];
  if (Object.prototype.toString.call(arr) !== '[object Array]') {
    var ct = 0;
    for (var k in arr) {
      if (ct === cursor) {
        return k;
      }
      ct++;
    }
    return false; // Empty
  }
  if (arr.length === 0) {
    return false;
  }
  return cursor;
}