JavaScript中没有块级作用域程序举例例证

	<script>
		var i = 10;
		function a(){
			alert(i);
		}
		//a();//output:10
	</script>
 
       <script>
		var i = 10;
		function a(){
			var i = 2;//在alert上可以输出2
			alert(i);
			//var i = 2;//在alert下因为未赋值所以输出undefined:不明确的变量
		}
		a();//output:undefined
<pre name="code" class="javascript">	</script>	<script>
		var i = 10;
		function a(){
			aler