JavaScript 错误 :Uncaught SyntaxError: Unexpected identifier

Question

我是 javascript 编码的初学者，当我在 Chrome 浏览器中加载第一个程序时遇到此错误，请教我它是什么

代码:

 var target;
 var select;
 var colors = ["brown", "cyan", "yellow", "red", "blue", "green", "black", "white", "purple", "pink"];
 var finished = false;

 function do_game() {
   var random_color = Math.floor(Math.random() * colors.length);
   target = colors[random_color];
 }
 while (!finished) {
   select = prompt("I am thinking of one of these colors\n\n brown,cyan,yellow,red,blue,green,black,white,purple,pink\n what color am i thinking of");
   finished = check_guess();
 }

 function check_guess() {
   if (select == target) {
     return true;
   } else {
     return false;
   }

 }

Answer 1

您提到的实际错误不会出现在您提供的代码中。我假设您在 HTML 属性中调用了 do_game ，例如 onclick 属性，并且那里有一个小拼写错误，例如放错位置的逗号或使用保留字， ...或许多其他语法问题之一。

你应该:

• 调用 do_game(您提供的代码中从未调用过它)
• 将循环放入该函数中

并进一步改进:

• 检测用户何时取消提示
• 使用局部变量而不是全局变量，并在其他地方需要时通过函数参数传递变量。真正的常量可以是全局的。
• 使用 let 和 const 而不是 var
• 避免使用 if(比较)return true else return false 模式。只需进行返回比较即可。
• 让用户知道他们猜对了
• 由于您已经有了一个颜色数组，因此不要在问题中再次将其作为文字字符串重复，而是重复使用该数组。

// The list of colors can be global, but the rest should be locally defined
const colors = ["brown", "cyan", "yellow", "red", "blue", "green", "black", "white", "purple", "pink"];

function do_game() {
    const random_color = Math.floor(Math.random() * colors.length);
    // Make your variables local to the function
    const target = colors[random_color];
    let finished = false;
    
    while (!finished) {
        // Actually declare `select`, or it will be global.
        // Reuse the variable with colors to build the question 
        //  (the commas will be inserted by the automatic conversion to string) 
        const select = prompt("I am thinking of one of these colors\n\n"
            + colors + ".\n\n What color am I thinking of?");
        // Exit game when prompt was cancelled
        if (select === null) return; 
        // Pass the necessary info to the other function (instead of using globals):
        finished = check_guess(select, target);
    }
    // Let the user know that they guessed it
    alert('You guessed it: ' + target);
}

function check_guess(select, target) {
    // No need to if-else a true/false, just return the comparison's result
    return select == target; 
}

// Start the game 
do_game();