javascript - 为什么提示框不断弹出“未定义”一词

Question

为什么提示框不断弹出说undefined？

function signup(name, age) {
    if (age < 20) {
        return alert("Sorry " + name1 + "! You are not old enough!");
    }
}

var name1 = prompt("What's your name?");
var age1 = prompt("What's your age?");

alert(signup(name1, age1));
alert("Let me get you started!");

标签： javascript

Answer 1