De-duplicate forward slashes in relative URLs

[MadLittleMods]

De-duplicate/collapse forward slashes when multiple pieces are provided,

Using [email protected]:

• urlJoin('/', '/') -> '/' ✔️
• urlJoin('/', '/sub', '/something') -> '/sub/something' ✔️
• urlJoin('/', '/sub/', '/something') -> '/sub/something' ✔️
• urlJoin('//', '/something') -> '/something' ✔️
• urlJoin('/', '/', '/something') -> '//something': ❌ expected '/something'
• urlJoin('/', '//', '/something') -> '//something': ❌ this isn't my exact use case but I guess this should also be '/something'

Is this behavior expected?

Related issues,

• v1.1.0 doesn't de-dupe "/" in relative URLs #16
• Trailing slash is not preserved #10

This issue was spawned from https://gitlab.com/gitlab-org/gitlab-selenium-server/merge_requests/10

[LvChengbin]

For this case, urlJoin('//', '/something') -> '/something, I think it should return '//something' for matching the rule of protocol-relative URL.

[hungtcs]

+1 same issues.

const prefix = '/a';
await import('url-join').then(join => join.default('http://localhost', prefix,  '/swagger'))
// out: 'http://localhost//swagger'

const prefix = '/doc';
await import('url-join').then(join => join.default('http://localhost', prefix,  '/swagger'))
// out: 'http://localhost/doc/swagger'