function test1(){
    console.log(arguments.callee)
    function test2(){
        console.log(arguments.callee)
    }
    test2()
}
test1()

function sum(n){
    if(n<=1){
        return 1
    }
    return n+sum(n-1)
}
var res=sum(10)
console.log(res)

运行结果