正则表达式匹配任何一个词，但准确的词

Question

i'm struggling figure out a regex. I want to replace a space with a dash but only if the following word matches either class or series .

I have tried the following:

/\s(?=[^\s]*(class|series)$)/gi

'  E-Class' => ' -E-Class'
'E Class'   => 'E-Class'
' E Class'  => ' E-Class'

Above is close, but if there is already a dash it puts one before, which it shouldn't.

Answer 1

我相信你应该只匹配课堂或系列之前的空间，而不是之前的每个空间，这样你就可以尝试这样的事情：

/\s(class|series)$/gi

Answer 2

设法弄清楚，这按预期工作：

/\\s(?=class|series)/gi

Answer 3

Since you have [^\\s]* (No-Spaces) inside your positive look ahead, every word which ends in class or series (like E-Class or abcdefclass ) matches your positive look ahead. If you only want to replace the space in front of class and series you can simply remove that and use /\\s(?=(class|series)$)/gi

Answer 4

Following regex does the job as described by the OP ...

/\\s(?=class|series)|\\s(\\w+-?)+(?=class|series)/gi .

Actually it's two separate regular expressions, one ( \\s(?=class|series) ) for the obviously simple case of matching the pattern of eg ' E Class' , the other one ( \\s(\\w+-?)+(?=class|series) ) for the more complex patterns such as eg ' E-Class' or ' Ee-ef-fooSeries' where the OP wants to "... replace a space with a dash but only if the following word [contains] either class or series " ( contains and not matches ; see my first comment above).

The regex' match result needs to be handled by a custom replacer function. A test case might look similar to the next provided one ...

 const testEntries = [ // OP's request. [' E-Class', ' -E-Class'], ['E Class', 'E-Class'], [' E Class', ' E-Class'], // Bonus test. [' Ee-eClass', ' -Ee-eClass'], [' Ee-ef-Class', '-Ee-ef-Class'], [' Ee-ef-fooSeries', ' -Ee-ef-fooSeries'], ]; const regX = (/\\s(?=class|series)|\\s(\\w+-?)+(?=class|series)/gi); function didPassTest([value, expectedValue]) { return ( value.replace(regX, (match) => '-' + match.trim() ) === expectedValue ); } console.log( 'testEntries.every(didPassTest) ?..', testEntries.every(didPassTest) );