3种方式

<script>
	function fun1(x,y){
		return x+y;
	}

	var fun2=function(x,y){
		return x+y;
	}

	var fun3=new Function("x","y","return x+y");

	document.write(fun1(5,6));
	document.write(fun2(5,6));
	document.write(fun3(5,6));
</script>

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