How can I write a JavaScript regular expression to allow only letters and numbers?

Question

I wish to allow both upper case and lower case. I have tried

'k abBcdi #!129'.replace(/^[A-Za-z0-9]/g,'')

But it's not give me the correct answer

Answer 1

您需要在方括号内使用NOT运算符（ ^ ）：

/[^A-Za-z0-9]/g

Answer 2

Also use [^0-9A-z] instead. It probably has little to no performance effect, but it is slightly shorter and prettier.

Edit:Per a comment above, are you trying to find all letters and numbers and replace them or remove everything that's not a letter and number?

Answer 3

If you don't explicitly need to use the not ^ operator, you could simply use a special character to identify all non-alphanumeric characters:

'k abBcdi #!129'.replace(/[\W]/g,'')

Or, given that \\W allows the underscore ( _ ) it might be preferred to use:

'k abBcdi #!129'.replace(/(\W+)|(_)/g,'')

References:

• JavaScript Regular Expressions .