CODEWITHSUNDEEP
regeximageurlregex-look-ahead
linjunchao
linjunchao

Reputation: 97

Using negative lookahead in RegExp to correctly match image URLs wrapped in [img] tags?

Negative lookahead to match itself in RegExp

I want to use a RegExp to match an image url that will have two cases:

The first case it is a normal image URL, ending with .png and may contain some query string, at which point the RegExp will match it in its entirety.

https://test.com/cat.png?pkey=abcd

In the second case, the URL is wrapped in an [img][/img] tag, the RegExp will be expected not to any string.

[img]https://test.com/cat.png?pkey=abcd[/img]

Now I have written this regular expression, it works great on the first case

(https:\/\/.*?\.png(?:\?[\w&=_-]*)?)(?!\[)

however it does not work with the second case, it will still be matched up to the penultimate character of the URL. How can I modify my RegExp to achieve my goal?

Here's RegExp link: https://regexr.com/7eohf

Upvotes: 3

Views: 75

Answers (1)

logi-kal
logi-kal

Reputation: 7880

Try to ancitipate the lookahead immediately after .png:

(https:\/\/.*?\.png(?!\S*\[)(?:\?[\w&=_-]*)?)

Where \S matches any character that is not a space (you can replace it as you wish).

See a demo here.

Alternatively, you can impose that the last character matched is not followed by [?\w&=_-]:

(https:\/\/.*?\.png(?:\?[\w&=_-]*)?)(?![?\w&=_-]|\[)

Upvotes: 3

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