发表于 | 阅读次数:
字数统计: 162 | 阅读时长 ≈ 1

作为生成器函数参数发送值

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<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>Sending data to and recieving data from a generator</title>
		<link rel="stylesheet" href="../assert.css">
		<script src="../assert.js"></script>
	</head>
	<body>
		<script>
			function* NinjaGenerator(action) {
			  const imposter = yield ("Hatori " + action);

			  assert(imposter === "Hanzo",
			        "The generator has been infiltrated");

			  yield ("Yoshi (" + imposter + ") " + action);
		  	}
			 
			const ninjaIterator = NinjaGenerator("skulk");
			       
			const result1 = ninjaIterator.next();
			assert(result1.value === "Hatori skulk", "Hatori is skulking");

			const result2 = ninjaIterator.next("Hanzo");
			assert(result2.value === "Yoshi (Hanzo) skulk",
			       "We have an imposter!");
		</script>
	</body>
</html>

发表于 | 阅读次数:
字数统计: 148 | 阅读时长 ≈ 1

通过函数访问私有变量 而不是通过对象访问

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<!DOCTYPE html>
<html>
<head>
  <title>Private variables are accessed through functions and not through objects</title>
  <meta charset="utf-8">
  <script src="../assert.js"></script>
  <link rel="stylesheet" type="text/css" href="../assert.css">
</head>
<body>
	<script>
	  function Ninja() {
      var feints = 0;
      this.getFeints = function(){
        return feints;
      };
      this.feint = function(){
        feints++;
      };
    }
    var ninja1 = new Ninja();
    ninja1.feint();

    var imposter = {};
    imposter.getFeints = ninja1.getFeints;

    assert(imposter.getFeints () === 1,
          "The imposter has access to the feints variable!");
	</script>
</body>
</html>

发表于 | 阅读次数:
字数统计: 199 | 阅读时长 ≈ 1

对比上一个 使用const let 关键字

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<!DOCTYPE html>
<html>
<head>
  <title>Using const and let keywords</title>
  <meta charset="utf-8">
  <script src="../assert.js"></script>
  <link rel="stylesheet" type="text/css" href="../assert.css">
</head>
<body>
	<script>
    "use strict"
    const globalNinja = "Yoshi";

    function reportActivity(){
      const functionActivity = "jumping";

      for(let i = 1; i < 3; i++) {
          let forMessage = globalNinja + " " + functionActivity;
          assert(forMessage === "Yoshi jumping",
                 "Yoshi is jumping within the for block");
          assert(i, "Current loop counter:" + i);
      }

      assert(typeof i === "undefined" && typeof forMessage === "undefined",
            "Loop variables not accessible outside the loop");
      }

    reportActivity();
    assert(typeof functionActivity === "undefined"
        && typeof i === "undefined" && typeof forMessage === "undefined",
        "We cannot see function variables outside of a function");
  </script>
</body>
</html>

发表于 | 阅读次数:
字数统计: 233 | 阅读时长 ≈ 1

使用关键字var时 该变量时在距离最近的函数内部或是在全局词法环境中定义的

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<!DOCTYPE html>
<html>
<head>
  <title>Using the var keyword</title>
  <meta charset="utf-8">
  <script src="../assert.js"></script>
  <link rel="stylesheet" type="text/css" href="../assert.css">
</head>
<body>
	<script>
	  var globalNinja = "Yoshi";

    function reportActivity(){
      var functionActivity = "jumping";

      for(var i = 1; i < 3; i++) {
          var forMessage = globalNinja + " " + functionActivity;
          assert(forMessage === "Yoshi jumping",
                 "Yoshi is jumping within the for block");
          assert(i, "Current loop counter:" + i);
      }

      assert(i === 3 && forMessage === "Yoshi jumping",
            "Loop variables accessible outside of the loop");
      }
      
      // for 循环外部 仍然能够访问for循环中定义的变量

    reportActivity();
    assert(typeof functionActivity === "undefined"
        && typeof i === "undefined" && typeof forMessage === "undefined",
        "We cannot see function variables outside of a function");
	</script>
</body>
</html>

发表于 | 阅读次数:
字数统计: 129 | 阅读时长 ≈ 1

执行上下文来跟踪代码

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<!DOCTYPE html>
<html>
<head>
  <title>The creation of execution contexts</title>
  <meta charset="utf-8">
  <script src="../assert.js"></script>
  <link rel="stylesheet" type="text/css" href="../assert.css">
</head>
<body>
	<script type="text/javascript">
	  function skulk(ninja) {
      report(ninja + " skulking");
    }

    function report(message) {
      console.log(message);
    }

    skulk("Kuma");
    skulk("Yoshi");
	</script>
  <p>Outputs to the console (press F12)</p>
</body>
</html>