javascript简单链式调用案例分析

<script>
  window.$ = function (id) {
    return new _$(id);
  }
  function _$(id) {
    this.elements = document.getElementById(id);
  }
  _$.prototype = {
    constructor: _$,
    hide: function () {
      console.log('hide');
      return this;
    },
    show: function () {
      console.log('show');
      return this;
    },
    getName: function (callback) {
      if (callback) {
        callback.call(this, this.name);
      }
      return this;
    },
    setName: function (name) {
      this.name = name;
      return this;
    }
  }
  $('test').setName('helloworld').getName(function (name) {
    console.log(name);
  }).show().hide().show().hide().show();
</script>