javascript - 为什么此代码有时会使浏览器崩溃？

Question

任何人都可以向我解释为什么这段代码有时会进入无限循环(大概来自 while 循环)并导致浏览器窗口崩溃？是不是和while(userChoice != randNumber)有关，这还不够结束吗？

var check = function(userChoice) {
        while ((isNaN(userChoice)) || (userChoice > 100) || (userChoice < 1) || (userChoice %1 !== 0)) {
        userChoice = prompt("Choose a number between 1 - 100", "It must be a whole number!");
    }
};

var randNumber = Math.floor(Math.random() * 100 + 1);
var userChoice = prompt("Choose a number between 1 - 100");
console.log(userChoice);
check(userChoice);
//Above sorts out the computer choice and sets the rules for the user choice

while(userChoice != randNumber) {
    if (userChoice > randNumber) {
        userChoice = prompt("Your number is GREATER than the computer.", "Please re-choose a number between 1 - 100");
        check(userChoice);
    }
    else if (userChoice < randNumber) {
        userChoice = prompt("Your number is SMALLER than the computer.", "Please re-choose a number between 1 - 100");
        check(userChoice);
    }
}    

console.log("Your number matches! Congratulations!");

这是对我之前的一些代码的修改，这些代码会更频繁地崩溃。虽然上面的代码更稳定，但它仍然偶尔会崩溃，尽管我无法解释启动无限循环的确切过程。

旧代码如下: (作为优先事项，有人可以告诉我为什么会崩溃吗？我不明白为什么 while 循环在达到正确的数字时没有结束!)

main = function() {


var randNumber = Math.floor(Math.random() * 100 + 1);
var userChoice = prompt("Choose a number between 1 - 100");
while ((isNaN(userChoice)) || (userChoice > 100) || (userChoice < 1) || (userChoice %1 !== 0)) {
    userChoice = prompt("Choose a number between 1 - 100", "It must be a whole number!");
}
//Above sorts out the computer choice and sets the rules for the user choice

while(userChoice !== randNumber) {
    if (userChoice > randNumber) {
        userChoice = prompt("Your number is GREATER than the computer.", "Please re-choose a number between 1 - 100");
    }
    else if (userChoice < randNumber) {
        userChoice = prompt("Your number is SMALLER than the computer.", "Please re-choose a number between 1 - 100");
    }
}    

return("Your number matches! Congratulations!");

};
main();

Answer 1

“旧代码”的问题在于您在 while 条件中使用“严格相等比较”!==，除非满足以下条件，否则不会满足该条件:由于提示返回字符串值，因此您将 userChoice 转换为数字。如果您使用 != 代替，它就会起作用。

“新代码”的问题与闭包有关，在 check 函数内部创建了一个新的局部变量 userChoice 因为您传递了一个参数，这意味着检查内部的 userChoice 与您在外部声明的 userChoice 不同，您只需删除该参数并使用您定义的全局变量即可:

var check = function() {...}
... 
var userChoice = prompt("Choose a number between 1 - 100");
check();