正则表达式在正则表达式中匹配，但在javascript中不匹配？

Question

I am trying to find a regex that will work for validating URLs. I found this guy:

^(http|ftp|https)://[\w-]+(\.[\w-]+)+([\w.,@?^=%&:/~+#-]*[\w@?^=%&/~+#-])?$

Which worked pretty well when I tested it using regexpal , but when I actually plug it into my javascript it fails to match. Fiddle here.

I am testing against this URL:

http://s3.amazonaws.com/SomeShow/Podcasts/HouroneofWhatever234.mp3

Can anyone see why it would match in regexpal, but not when I try to use it in my javascript?

Answer 1

Use a regex literal:

/^(http|ftp|https):\/\/[\w-]+...$/

(you also have to escape the slashes to prevent the them to be interpreted as ending regex terminal symbol)

If you use a string, you have to escape every backslash, because the backslash is the escape characters in strings as well.

new RegExp("^(http|ftp|https)://[\\w-]+...$")

In your current expression, "[\\w-]+" will turn to [w]+ because \\w is not a valid escape sequence in strings.

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See: https://developer.mozilla.org/en-US/docs/JavaScript/Guide/Regular_Expressions#Creating_a_Regular_Expression