js0016

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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>