javascript 正则表达式仅在字符串中的符号使用一次时才匹配

Regex to match only if symbol in string used once

提问by Kosmetika

Maybe it's a simple question but today i'm a bit stucked with it.

也许这是一个简单的问题，但今天我有点被它困住了。

I need regex to match only if symbol %appeared once in a string..

只有当符号%在字符串中出现一次时，我才需要正则表达式来匹配..

for example:

例如：

/regexpForSymbol(%)/.test('50%') => true
/regexpForSymbol(%)/.test('50%%') => false

Thanks!

谢谢！

回答by Jerry

You could use:

你可以使用：

^[^%]*%[^%]*$

The anchors are there to ensure every character is covered, and you probably already know what [^%]does.

锚点是为了确保每个角色都被覆盖，你可能已经知道是什么了[^%]。

回答by melwil

Here you go. Don't expect everyone to make these for you all the time though.

干得好。不过，不要指望每个人都一直为你做这些。

^      # Start of string
[^%]*  # Any number of a character not matching `%`, including none.
%      # Matching exactly one `%`
[^%]*  # 
$      # End of string

回答by Niccolò Campolungo

You don't need regex.

你不需要正则表达式。

function checkIfOne(string, char) {
    return string.split(char).length === 2;
}

Usage:

用法：

var myString = "abcde%fgh",
    check = checkIfOne(myString, '%'); // will be true

回答by David Hellsing

You can use matchand count the resulting array:

您可以使用match和计算结果数组：

str.match(/%/g).length == 1