RegexdrillAlternation precedence: image file names
A regex exercise from Regexdrill. Solve it with a pattern box with live highlighting in your browser, checked against hidden test strings, and it is checked the moment you submit.
The task
The whole line must match. Match a file name made of word characters, a period and one of the lowercase extensions jpg, jpeg, png or gif.
What this exercise teaches
\w+\.(?:jpg|jpeg|png|gif) puts the alternatives in a group, so each one is reached only after the name and the period. The jpg branch is tried before jpeg, but photo.jpeg still passes: when jpg leaves text unmatched, the engine backtracks and tries the next alternative.
A hint if you get stuck
Without a group, \w+\.jpg|png means (\w+\.jpg) or (png). Group the extensions so the name and the period apply to all of them.
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