code: function pushEncodedKeyValuePair(pairs, key, val) {
    if (Array.isArray(val)) {
      return val.forEach(function(v) {
        pushEncodedKeyValuePair(pairs, key, v);
      });
    }
    pairs.push(encodeURIComponent(key)
      + '=' + encodeURIComponent(val));
  }
docs: Helps 'serialize' with serializing arrays.
  Mutates the pairs array.
  
  @param {Array} pairs
  @param {String} key
  @param {Mixed} val