Javascript trim double slashes

Question

I would like to trim //a/url/// to a/url . There are a few questions on Stackoverflow but they don't work, solves another problem or is too long and complex.

The code below is working and is based on Javascript regular expression: remove first and last slash

function trimSlashes(str) {
  str = str.replace(/^\/|\/$/g, '');
  return str.replace(/^\/|\/$/g, '');
};

However it's not very nice to duplicate code like that. How would a regex look like that takes care of double slashes as well?

Testcase

let str1 = trimSlashes('/some/url/here/');
let str2 = trimSlashes('//some/other/url/here///');

Expected result

some/url/here
some/other/url/here

Wishlist

• Just a single regex
• Shorter or faster is better

Answer 1

Here's another variation without a regex but with a functional flair. I don't know about the performance but I had fun writing it and seems less cryptic.

const newString = '//some/other/url/here///'
.split('/')
.filter(s => s)
.join('/')

Edit:

Just ran some perf tests and this is slower than a regex but it might be insignificant if used sparingly.

https://jsperf.com/regex-vs-functional/1

Answer 2

replace(/^\\/+|\\/+$/g, '') is what you're looking for:

Result with both test cases:

> '/some/url/here/'.replace(/^\/+|\/+$/g, '');
"some/url/here"

> '//some/other/url/here///'.replace(/^\/+|\/+$/g, '');
"some/other/url/here"

Explained:

^\/+  # one or more forward slashes at the beginning
|     # or
\/+$  # one or more forward slashes at the end

Answer 3

With regexes you must be careful of unintended matches. for example do you want to trim the slash when the text is "// and this is a comment in some line of text//"?

If you don't want to trim things like that down you need to be a little more careful with the regex, how about this?

let regex = /^\/+([\w\/]+?)\/+$/;
let matches = regex.exec("//some/other/url/here///");
let url = matches[1];

https://regex101.com/r/K8CnxP/1