Question

标题是自我解释我有这个JS代码（回到基础）非常简单，但我不能为我的生活弄清楚为什么我不会跑。我所知道的是开发者控制台说出了意想不到的令牌＆＃34; {＆＃34;在第21行，但那是打开我的if语句的原因。

enter code here
<!Doctype html>
<html land="en">
   <head>
       <meta charset="utf-8" />
      <title>Chapter 2, Example 7</title>
   </head>
   <body>
       <script type="text/javascript">
         var myAge = parseInt(prompt ("Enter your age", 30),10);

         if (myAge >= 0 && myAge <= 100) {
            document.write("myAge is between 0 and 10<br />");
         }
         if (!(myAge >= 0 && myAge <= 10) ) {
            document.write("myAge is NOT between 0 and 10<br />");
         }
         if (myAge >= 80 || myAge <= 10) {
            document.write("myAge is 80 or above OR 10 or below<br />");
         }

         if ( (myAge >= 30 && myAge <= 39 || (myAge >= 80 && myAge <= 89) ) {
            document.write("myAge is between 30 and 39 or myAge is " +
            "is between 80 and 89");
        }
        </script>
      </body>
   </html>

Answer 1

你错过了这一行的括号

if ((myAge >= 30 && myAge <= 39 || (myAge >= 80 && myAge <= 89)) {

应该是

if ((myAge >= 30 && myAge <= 39) || (myAge >= 80 && myAge <= 89)) {

Answer 2

变化

if ( (myAge >= 30 && myAge <= 39 || (myAge >= 80 && myAge <= 89) ) {

到

if ( (myAge >= 30 && myAge <= 39) || (myAge >= 80 && myAge <= 89) ) {

或者如果您愿意，可以使用关键字operator precedence：

if (myAge >= 30 && myAge <= 39 || myAge >= 80 && myAge <= 89) {

并略微提示

if (myAge >= 0 && myAge <= 100) { // <-- or this should be 10 ...?
    document.write("myAge is between 0 and 10<br />");
} //                                       ^^
//                               should be 100?

无法弄清楚这个简单的JS代码有什么问题

2 个答案: