闭包常见应用场景

<script type="text/javascript">
  function wait(message) {
    setTimeout(function timer() {
      //延时函数回调函数timer
      //timer内部函数具有涵盖wait函数作用域的闭包，还有对变量message的引用
      console.log(message);
    }, 1000)
  }
  wait('闭包函数应用')
</script>

<script type="text/javascript">
  function test() {
    var a = 0;
    //事件监听器 保持对test作用域的访问
    $('ele').on('click', function() {
      a++;
    });
  }
</script>

<script type="text/javascript">
  !function() {
    var localData = "localData here";
    var url = "http://www.baidu.com/";
    //ajax使用了localData，url
    $.ajax({
      url: url,
      success: function() {
        // do sth...              
        console.log(localData);
      }
    });
  }();
</script>

<script type="text/javascript">
  var foo = (
    function Module() {
      var something = 'cool';
      var another = [1, 2];

      function doSomething() {
        console.log(something)
      }

      function doAnother() {
        console.log(another.join(','))
      }
      return {
        doSomething: doSomething,
        doAnother: doAnother
      }
    }
  )();
  foo.doSomething();
  foo.doAnother();
</script>