本文详细解析了JS执行顺序测试，包括从上到下依次执行的特性，head中代码在内容加载前执行的特点，以及body中代码执行顺序的实例。
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<title>js执行顺序测试</title>
<wbr><wbr><wbr><wbr><span style="color:red"><script type="text/javascript"><br><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr> alert("body</wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></span><span style="color:red">加载之前运行</span><span style="color:red">1");<br><wbr><wbr><wbr><wbr> </script></wbr></wbr></wbr></wbr></span></wbr></wbr></wbr></wbr>
<wbr><wbr><wbr><wbr><span style="color:red"><script type="text/javascript"><br><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr> alert("body</wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></span><span style="color:red">加载之前运行</span><span style="color:red">2");<br><wbr><wbr><wbr><wbr> </script></wbr></wbr></wbr></wbr></span></wbr></wbr></wbr></wbr>
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<body>
<wbr><wbr><wbr><wbr><strong>aaa<br></strong><wbr><wbr><wbr><wbr><span style="color:red"><script type="text/javascript"><br><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr> alert("body</wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></span><span style="color:red">加载之后运行</span><span style="color:red">1");<br><wbr><wbr><wbr><wbr> </script><br></wbr></wbr></wbr></wbr></span><wbr><wbr><wbr><wbr><strong>bbb<br></strong><wbr><wbr><wbr><wbr><span style="color:red"><script type="text/javascript"><br><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr> alert("body</wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></span><span style="color:red">加载之后运行</span><span style="color:red">2");<br><wbr><wbr><wbr><wbr><wbr> </script></wbr></wbr></wbr></wbr></wbr></span></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>
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从这个例子中我们看出：
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①js从上到下依次执行
②放在head中的js，在下面内容未加载之前得到执行，注意和onload事件区分
③在body中代码执行的顺序是
aaa->弹出"body加载之后运行1"->bbb->弹出"body加载之后运行2"
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