JavaScript字符串仅在开始时与使用indexOf匹配? [英] JavaScript string matching only at the start versus using indexOf?

问题描述

我当前正在匹配用户输入，如下所示:

I currently am matching user input as follows:

user_input = "upload a file"

if ( "upload a file".indexOf(user_input.toLowerCase()) > -1 ) {}

这工作正常，但问题是，它与我不想要的文件"匹配.我希望只有在开头正确的情况下才能匹配.

This work fine but the problem is, it matches "a file" which I don't want. I want it to only match if the beginning is correct.

这应该匹配:

"upload"
"u"
"upload a"

这不应该匹配，因为字符串从一开始就不匹配:

This should not match, because the string does not match from the start:

"a"
"file"

关于如何使用indexOf实现这一目标，是否有任何建议?

Are there any suggestions on how to make this happen with indexOf?

推荐答案

indexOf返回匹配的索引，因此，如果要在开始时测试它是否匹配，只需检查它是否返回0

indexOf return the index of the match, so if you want to test if it match at the beginning just check if it returns 0

user_input = "upload a file"
if ( "upload a file".indexOf(user_input.toLowerCase()) == 0 ) {}

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