当我的console.log类型的函数返回一个对象时，它的类型为undefined。 我不明白为什么

Question

I can't understand why the result of this code is undefined?

function f() {
    return
    {
        x: 0
    };
}
console.log(type of f());

Answer 1

typeof is a single word. Also, you are invoking your function, thus you are evaluating it's returned value, which is undefined in your code because of automatic semicolon insertion.

from https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/return

The return statement is affected by automatic semicolon insertion (ASI). No line terminator is allowed between the return keyword and the expression.

 function f() { return //this is treated as though it had a ; { x: 0 }; } console.log(typeof f()); console.log(typeof f); 

 function f() { return { x: 0 }; } console.log(typeof f()); console.log(typeof f);