JavaScript中的Else if和Else
[英]Else if and Else in JavaScript
问题描述
I wrote a small javascript code, but it has a problem, the page can not show anything. 
我写了一个小的javascript代码，但是有一个问题，该页面无法显示任何内容。 I think the problem is in the line "else if..." or "else...", because if I comment these two lines, the code runs without any problem 我认为问题出在“ else if ...”或“ else ...”行中，因为如果我注释这两行，则代码可以正常运行
<html>
<head>
<script language="javascript">
var var1 = window.prompt("please input");
var var2 = window.prompt("please input2");
var1 = parseFloat(var1);
var2 = parseFloat(var2);
if (var1< var2) {document.writeln("the second number is bigger")};
else if (var1> var2) {document.writeln("the first number is bigger")};
else {document.writeln("They are the same")};
</script>
</head>
<body>
</body>
</html>
5 个解决方案
解决方案1
3 2015-12-25 19:00:15
Your javascript should be like this 您的JavaScript应该是这样的
var var1 = window.prompt("please input"); var var2 = window.prompt("please input2"); var1 = parseFloat(var1); var2 = parseFloat(var2); if (var1 < var2) { document.writeln("the second number is bigger"); } else if (var1 > var2) { document.writeln("the first number is bigger"); } else { document.writeln("They are the same"); }
解决方案2
1 2015-12-25 18:59:25
Should be: 应该：
<html>
<head>
<script language="javascript">
var var1 = window.prompt("please input");
var var2 = window.prompt("please input2");
var1 = parseFloat(var1);
var2 = parseFloat(var2);
if (var1 < var2) {
document.writeln("the second number is bigger");
}
else if (var1 > var2) {
document.writeln("the first number is bigger");
}
else {
document.writeln("They are the same");
}
</script>
</head>
<body>
</body>
</html>
your semi colons were wrong 你的半冒号错了
解决方案3
1 已采纳 2015-12-25 19:02:24
Try removing the semicolon, ; 尝试删除分号; , from after the brackets of your if statements : ，从if statements的括号后面开始：
if (var1< var2) {document.writeln("the second number is bigger")}
else if (var1> var2) {document.writeln("the first number is bigger")}
else {document.writeln("They are the same")}
Have a look at this SO answer: https://stackoverflow.com/a/17036218/4206206 看看这个SO答案： https : //stackoverflow.com/a/17036218/4206206
Essestially, a semicolon isn't used to end a group of statements, but rather to end a single statement. Essestially，分号不使用结束一组语句，而是结束一个语句。
A point with your code, if you're using HTML5 you don't need the language="javascript" in your script tags: 代码要点，如果您使用的是HTML5，则不需要在脚本标签中使用language="javascript" ：
<script language="javascript">
Can become simply 可以变得简单
<script>
解决方案4
0 2015-12-25 19:01:05
if (var1< var2) {document.writeln(" ... ")};
^
Your semicolons at the end of your if, else if, and else blocks are your issue. 您在if，else if和else块末尾的semicolons是您的问题。 They are prematurely ending your if blocks. 他们过早地结束了if块。
解决方案5
-1 2015-12-25 19:01:16
Just make sure you parseFloat before you compare, because it just compares as string, and remember, 10 comes before 2, so by string 10 < 2 ! 只需在比较之前确保您parseFloat ，因为它只是作为字符串进行比较，并且请记住，10在2之前，所以按字符串10 < 2 ！ And you don't need the ; 而且您不需要; at the end: 在末尾：
var var1 = window.prompt("please input");
var var2 = window.prompt("please input2");
var1 = parseFloat(var1);
var2 = parseFloat(var2);
if (var1 < var2) {
document.writeln("the second number is bigger");
} else if (var1 > var2) {
document.writeln("the first number is bigger");
} else {
document.writeln("They are the same");
}
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