phpjs/functions/array/in_array.js

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function in_array(needle, haystack, argStrict) {
  //  discuss at: http://phpjs.org/functions/in_array/
  // original by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // improved by: vlado houba
  // improved by: Jonas Sciangula Street (Joni2Back)
  //    input by: Billy
  // bugfixed by: Brett Zamir (http://brett-zamir.me)
  //   example 1: in_array('van', ['Kevin', 'van', 'Zonneveld']);
  //   returns 1: true
  //   example 2: in_array('vlado', {0: 'Kevin', vlado: 'van', 1: 'Zonneveld'});
  //   returns 2: false
  //   example 3: in_array(1, ['1', '2', '3']);
  //   example 3: in_array(1, ['1', '2', '3'], false);
  //   returns 3: true
  //   returns 3: true
  //   example 4: in_array(1, ['1', '2', '3'], true);
  //   returns 4: false

  var key = '',
    strict = !! argStrict;

  //we prevent the double check (strict && arr[key] === ndl) || (!strict && arr[key] == ndl)
  //in just one for, in order to improve the performance 
  //deciding wich type of comparation will do before walk array
  if (strict) {
    for (key in haystack) {
      if (haystack[key] === needle) {
        return true;
      }
    }
  } else {
    for (key in haystack) {
      if (haystack[key] == needle) {
        return true;
      }
    }
  }

  return false;
}