regex JavaScript with repeating string

Question

I would like to parse with regex files with the following format in order to retrieve content1a, content1b,content2a,content2b, etc ...

===
content1a
===
content1b
===
content2a
===
content2b

Important : the end of file does not contain ===

This regex does almost the job :

/[===[\s\S]*?===[.]*/g

but does not retrieve the last content (content2b)

Thank you for helping

... for the provided use case something like ... str.match(/^(?!\=).*$/gm) ... already should be sufficient enough. — Peter Seliger
– Peter Seliger, Commented Jun 25, 2020 at 10:11

The fourth bird · Accepted Answer · 2020-06-25 08:54:48Z

4

The pattern that you tried uses a character class, which can also be written as [\s\S]*?=== or ([^]*?)===

It expects === to be there at the end, that is why is does not match the last content.

But if you have for example 5 times an equals sign ===== you will also match the last 2 equals signs, so you could add a newline to prevent that.

Instead of using [\s\S]*? You could use a capturing group to capture all lines that do not start with ===

^===\n((?:(?!===\n).*\n?)*)

Regex demo

const regex = /^===\n((?:(?!===\n).*\n?)*)/gm;
const str = `===
content1a
===
content1b
===
content2a
content2a
content2a
===
content2b`;
let m;

while ((m = regex.exec(str)) !== null) {
  // This is necessary to avoid infinite loops with zero-width matches
  if (m.index === regex.lastIndex) {
    regex.lastIndex++;
  }
  console.log(m[1]);
}

edited Jun 25, 2020 at 8:54

answered Jun 25, 2020 at 7:47

The fourth bird

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2 Comments

tit Over a year ago

Same : perfect in php, almost in js. Thanks

The fourth bird Over a year ago

@tit I have added a js example

Liam · Accepted Answer · 2020-06-25 07:37:00Z

3

You don't need a regex you can just split the string

const str = `===
content1a
===
content1b
===
content2a
===
content2b`;

const contents = str.split('===\n').filter(f => f !== "");

console.log(contents);

answered Jun 25, 2020 at 7:37

Liam

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3 Comments

tit Over a year ago

this is not a regex, but nice!

Liam Over a year ago

No and by not being a regex it's easier to read and probably marginally more efficient. "Some people, when confronted with a problem, think "I know, I'll use regular expressions." Now they have two problems." (though I don't really subscribe to this opinion myself)

Peter Seliger Over a year ago

I would change the split value to (/\n*===\n/); thus the filtered values from the split-list will not anymore be terminated by \n.

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