Regex isn't matching on Javascript .split() but does match on testing tool

Question

I have this code. I am trying to match on .mono-50, where 50 can be any number.

imageUrl = 'http://example.com/media/image.mono-50.png';
imageUrlSplit = imageUrl.split('/.mono-\d+/');
console.log(imageUrlSplit);

This does not match, but does match on my testing tool, regexr.com

http://regexr.com/3e55b

I have done many variations on it including the following.

.split('/.mono\-\d+/');
.split('/\.mono\-\d+/');
.split('/.mono-\d+/g');
.split('/.mono\-\d+/g');
.split('/\.mono\-\d+/g');

All of these work in the tool, but none in Javascript. Am I misunderstanding something on how .split() treats Regex?

I have seen this question, but it has not helped me solve this issue.

Javascript split regex question

Remove the single quotes, as you're splitting on a string rather than a pattern. — John
– John, Commented Aug 31, 2016 at 22:15
@Trey: Not only. The dot must be escaped, too. OP is not sure whether it must be escaped or not. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Aug 31, 2016 at 22:16
@WiktorStribiżew correct, but he has escaped them in some of his attempts so I didn't mention it — John
– John, Commented Aug 31, 2016 at 22:17
'/\.mono\-\d+/g' -> the literal string that starts with forward slash contains "mono" and finishes on forward slash and "g". /\.mono\-\d+/g the regex that matches a pattern that contains a literal dot, followed by "mono" dash and any number of digits. — VLAZ
– VLAZ, Commented Aug 31, 2016 at 22:18
If the dot is unescaped, then 'http://example.com/media/demono-60/image.mono-50.png' would get split incorrectly. @Vld: the global behavior is default with split(). A second argument controls that side of splitting. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Aug 31, 2016 at 22:19

Wiktor Stribiżew · Accepted Answer · 2016-08-31 22:14:46Z

2

You need to use a regex literal notation (when the regex literal is put inside quotes it becomes a regular string literal, and split uses this text as a literal string, not a pattern) and escape the dot since an unescaped dot in a regex pattern matches any character (but a newline):

imageUrlSplit = imageUrl.split(/\.mono-\d+/);
                               ^^^        ^

See demo:

imageUrl = 'http://example.com/media/image.mono-50.png';
imageUrlSplit = imageUrl.split(/\.mono-\d+/);
console.log(imageUrlSplit);

answered Aug 31, 2016 at 22:14

Wiktor Stribiżew

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