ElseIf与ElseIf [英] ElseIf vs Else If

问题描述

多年来，我一直在使用Else If在VBScript中进行编码...

For years now I've been using Else If to code in VBScript...

If a = b Then
    ...
Else If a = c Then
    ...
End If

似乎可以按要求工作.除了使用ElseIf的MSDN，我还看到了很多使用Else If的网站.

Which seems to work as required. I've also seen many sites on the web that use Else If, excepting MSDN that uses ElseIf.

ElseIf与Else If之间是否有区别?

<罢工> 这是我之前编写的，可以通过Classic ASP正常工作.

Here's one I coded earlier that's working just fine through Classic ASP:

If IsDate(wD) Then
    wS = wD
Else If wD&"" <> FormatDisplayDate(wS) Then
    wS = WeekStart(Date())
    wD = FormatDisplayDate(wS)
End If

这是别人写的一段较旧的代码片段...

Here's a snippet from an older piece of code, written by someone else...

if opip = "IP" then
    opip = "In Patient"
Else If opip = "OP" then
    opip = "Out Patient"
End If

这些都不是通过编译器运行的，但是都可以解释.

None of these are run through a compiler, however, it's all interpreted.

忽略那个垃圾-我搞砸了搜索并在IDE中进行了替换.

Ignore that junk - I messed up a search and replace in the IDE.

推荐答案

该示例代码无法编译并产生编译错误

That example code doesn't compile and produces the compilation error

Microsoft VBScript编译错误:预期为结束"

Microsoft VBScript compilation error: Expected 'End'

如我所料(如 @ ekkehard-horner

as I'd expect (as @ekkehard-horner point's out in the comments).

除了

I've never known ElseIf to work any other way then detailed in MSDN. The only thing I can think of is you are writing it as a nested If statement.

If a = b Then
    ...
Else If a = c Then
    ...
End If
End If

看起来真的很丑，但是和写作一样

which looks really ugly but is the same as writing

If a = b Then
    ...
Else
    If a = c Then
        ...
    End If
End If

此方法的问题是，您最终在嵌套的If语句上遇到未处理的条件.例如，如果a = d会发生什么?

Problem with this approach is you end up with an un-handled condition on the nested If statement. What happens if a = d for example?

您需要确保嵌套的If捕获了ElseIf语句不需要的额外条件.

You would need to make sure your nested If caught the extra condition which isn't needed with an ElseIf statement.

If a = b Then
    ...
Else
    If a = c Then
        ...
    Else
        ...
    End If
End If

ElseIf方法应该是；

If a = b Then
    ...
ElseIf a = c Then
    ...
Else
    ...
End If

---

有趣的沉思，由

---

Interesting musing by @eric-lippert (one of the programmers behind the VBScript compiler) in the sea of comments...well worth a read. I certainly learned something.

这篇关于ElseIf与ElseIf的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！