JavaScript replace regex by regex

Question

I have some text, which contains a markdown link:

var text = 'some text some text [some text](link.md) some text some text';

I want to change that to

var newText = 'some text some text [some text](link.html) some text some text';

basically, changing the .md to .html, but only if it's a valid markdown link. A valid markdown link is []() with text between it.

Currently I have to following regex: /\[.*\]$.*.md$/g.

However, how will I perform a regex replace in Javascript (if the regex above matches, replace .md with .html)?

Tim Biegeleisen · Accepted Answer · 2018-04-16 02:03:11Z

3

Try this replacement:

var text = '[some text](link.md)';
console.log("Before:\n" + text);
text = text.replace(/(\[[^\]]+\])\(([^\)]+).md\).*/, "$1($2.html)");
console.log("After:\n" + text);

answered Apr 16, 2018 at 2:03

Tim Biegeleisen

526k32 gold badges323 silver badges399 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

ibrahim mahrir · Accepted Answer · 2018-04-16 02:04:59Z

2

First, you should use non-greedy mode *? instead of the gready one *. Then you should group the texts and use those groups to generate a new url:

str = str.replace(/\[(.*?)\]\((.*?).md\)/g, function(match, text, href) {
    return "[" + text + "](" + href + ".html)";
});

Shorter using an arrow function:

str = str.replace(/\[(.*?)\]\((.*?).md\)/g, (match, text, href) => 
    "[" + text + "](" + href + ".html)"
);

Example:

var text = '[some text](link.md)';


text = text.replace(/\[(.*?)\]\((.*?).md\)/g, (m, text, href) => "[" + text + "](" + href + ".html)");

console.log(text);

edited Apr 16, 2018 at 2:04

answered Apr 16, 2018 at 2:01

ibrahim mahrir

31.8k5 gold badges50 silver badges78 bronze badges

1 Comment

Mark Over a year ago

I was writing and answer using $1 and $3 but I quit in shame after seeing this lovely example clarity.

Michael Chaney · Accepted Answer · 2018-04-16 14:04:21Z

0

You could use a lookbehind:

text.replace(/(?<=\[.*?\])\((.*)\.md\)/, "($1.html)")

It's possible to do it without one by capturing the first part.

Edit:

There are two minor changes to make this work with multiple items in a string. First, add the obvious "g" flag to the regex. But, secondly, make the captured match non-greedy:

text.replace(/(?<=\[.*?\])\((.*?)\.md\)/g, "($1.html)")

As others have pointed out, you can capture the text in the square brackets and also substitute it, but this is a perfect example of using lookbehinds.

edited Apr 16, 2018 at 14:04

answered Apr 16, 2018 at 2:04

Michael Chaney

3,04922 silver badges27 bronze badges

3 Comments

Mark Over a year ago

This seems to only work on the last instance in a string like '[some text](link.md) [some other text](anotherlink.md) '

Tim Biegeleisen Over a year ago

This code doesn't appear to be working. I seem to recall that you can't use a loosbehind for a replacement (I also thought of doing this here).

Michael Chaney Over a year ago

It works in the latest version of Chrome. They added lookbehind support recently to Javascript.

Collectives™ on Stack Overflow

JavaScript replace regex by regex

3 Answers 3

Comments

1 Comment

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

1 Comment

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related