demos/closures.html

<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
</head>

<body>
  <p>不断单击【click】按钮</p>
  <button id="click_button">Click</button>
  <script>
    function f() {
      var str = Array(10000).join('#');
      var foo = {
        name: 'foo'
      }
      function unused() {
        var message = 'it is only a test message';
        // str = 'unused: ' + str;
      }
      function getData() {
        return 'data';
      }
      return getData;
    }

    var list = [];
    
    document.querySelector('#click_button').addEventListener('click', function () {
      list.push(f());
    }, false);
  </script>
</body>

</html>