Array flatten

gistfile1.txt

function flatten(array, isShallow, callback, thisArg) {
      var index = -1,
          length = array ? array.length : 0,
          result = [];

      // juggle arguments
      if (typeof isShallow != 'boolean' && isShallow != null) {
        thisArg = callback;
        callback = !(thisArg && thisArg[isShallow] === array) ? isShallow : undefined;
        isShallow = false;
      }
      if (callback != null) {
        callback = lodash.createCallback(callback, thisArg);
      }
      while (++index < length) {
        var value = array[index];
        if (callback) {
          value = callback(value, index, array);
        }
        // recursively flatten arrays (susceptible to call stack limits)
        if (isArray(value)) {
          push.apply(result, isShallow ? value : flatten(value));
        } else {
          result.push(value);
        }
      }
      return result;
    }