How to handle javascript variable scope in different browsers_javascript skills

1. About prototype: prototype here is a feature of javascript, not the famous prototype framework:

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2. About Variable scope, and the different handling of js by IE and Firefox, here are a few examples, some of which are notes I saw from elsewhere, and some of which I dug out myself.
2.1

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2.2

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2.3: <button id="thebutton" onclick="click_handler()"></button>
... Click me!

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2.4 <button id="thebutton" onclick="click_handler(this)"></button>
... Click me!

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<button id="thebutton" onclick="click_handler(this)">2.5 </button>
Click me!

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] <button id="thebutton" onclick="click_handler(this)"></button>2.6
Click me!

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If you need to introduce external Js, you need to refresh to execute ]<button id="thebutton" onclick="click_handler(this)"> </button>2.7
Click me!

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2.8 

<button id="thebutton" onclick="click_handler(this)">Click me!</button> <script type="text/javascript"> function real_func() { alert(this); } function btn_click(){ setTimeout(real_func,100); } function addhandler() { the_button = document.getElementById('thebutton'); the_button.onclick = btn_click; } window.onload = addhandler; //result [undefined] </script>
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2.9 

<button id="thebutton" onclick="click_handler(this)">Click me!</button> <script type="text/javascript"> Function.prototype.bind = function(obj) { var method = this, temp = function() { return method.apply(obj, arguments); }; return temp; } var real_func=function() { alert(this); } function btn_click(){ setTimeout( real_func.bind(this),100); } function addhandler() { the_button = document.getElementById('thebutton'); the_button.onclick = btn_click; } window.onload = addhandler; //result [undefined] </script>
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2.10 

<script> //** variables need to be defined alert(document); // [object HTMLdocument] alert(window.document); // [object HTMLdocument] alert(window.face); //pretty var face="pretty"; alert(face); //pretty alert(window.face); //pretty alert(window.sock); //undefined alert(sock); // ERROR: sock not defined </script>
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2.11

<script type="text/javascript"> function method() { var window={}; alert(window.location); } alert(window.location); method(); alert(window.location); </script>
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2.12

<script type="text/javascript"> var window={};//ERROR:非法赋值! // this works in IE,but throw an Exception in firefox alert(window.location); </script>
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2.13

<script type="text/javascript"> /** 这是一段很让人恼火的代码 可以禁用alert */ window.alert("hello world"); window.alert=function(str){ document.write(str); }; alert("hello world"); window.alert("hello world"); </script>
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2.14:

注意这三个html文件的结果有什么不同.
a.html: 

<script type="text/javascript"> alert(sock); function sock() { alert("function sock executed!"); } alert(sock); </script>
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b.html:

<script type="text/javascript"> alert(sock); var sock=function() { alert("function sock executed!"); } alert(sock); </script>
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c.html:

<script type="text/javascript"> // 这里并不弹出"undefined" // 有点偏心啊! alert(sock); </script>
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2.15

看看IE,firefox下分别运行有何不同:

<script type="text/javascript"> Object.prototype.hello=function(){ alert("hello"); } window.hello(); </script>
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