How to pluck the second value in a url after the first slash, in a string that could have many slash-CodePudding

I know there are countless regex questions out there, but I was unable to find one that fits my situation.

Suppose I have the following pathname:

/u/some_user/create/initial

How can I extract 'some_user' from this string?

I got pretty close with this:

const pathname = '/u/some_user/create/initial';

const result = pathname.match(/(\/u\/)(.{1,}\/)(. )/);

console.log('result', result);

This could potentially work if the string was '/u/some_user/create' -- It would return some_user/, and I could filter out the slash at the end. But if the string has more slashes, as above, then this just returns 'some_user/create/'.

How can I achieve plucking out just 'some_user'?

CodePudding user response：

You can use a capture group and a negated character class:

\/u\/([^/] )

Explanation

\/u\/ Match /u/
( Capture group 1
- [^/] Match 1 characters other than / using a negated character class.
) Close group 1

See a regex101 demo.

const regex = /\/u\/([^/] )/;
[
  "/u/some_user/create/initial",
  "/u/some_user/create",
  "test/123/u/some_user/a/b/c"
].forEach(s => {
  const m = s.match(regex);
  if (m) {
    console.log(m[1]);
  }
});

If you don't want to cross newlines, and there has to be a / after some_user:

\/u\/([^/\s] )\/

See another regex 101 demo.

CodePudding user response：

If you don't care about legacy browser support, which includes Safari and any browser installed on Mac/iOS, then this would work:

/(?<=^\/u\/)[^\/] /

var regexp = /(?<=^\/u\/)[^\/] /;

console.log( `/u/some_user/create/initial`.match( regexp ) );
console.log( `/u/`.match( regexp ) );
console.log( `/wrong/format/url`.match( regexp ) );
console.log( `/u/another_user/create/initial`.match( regexp ) );

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

CodePudding user response：

Not withstanding the request for a regular expression, the specific problem is easily solved with either of two common string methods.

string.split

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/split

Returns an array of substrings demarked according to any character or characters provided as an argument. By splitting the string at each of the slashes, the required string is element[2] of the resulting array (since element [0] will be empty -being derived from 0 characters before the first "/").

viz:

const url = "/u/some_user/create/initial";

requiredString = url.split("/")[2];

console.log(requiredString); // "some_user";

string slice

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/slice

Where the position, either numerically or by reference to known bounding test, of the target substring is available, string.slice provides an easy method to extract the required substring.

In this example bounding text parts are used to extract the required field:

const url = "/u/some_user/create/initial";

beforeText = "/u/";
afterText = "/create";

let requiredString = url.slice(url.indexOf(beforeText) beforeText.length, url.indexOf(afterText));

console.log(requiredString); // "some-user"

Both of these methods are reliable core javascript, supported by all interpreters.