var foo=function(x,y){ return x-y } function foo(x,y){ return x+y } var num=foo(1,2) 执行代码后输出结果为:-1; 代码会被JS编译器解析成: //variable hoisting变量提升 var foo;//foo#1 var num; //function declaration hoisting函数声明提升 function foo(x,y){//foo#2 return x+y; } //function expression NOT hoist...