Normalize path for windows os

[xcatliu]

This pr fixed the path issue in windows os.

When exec parcel build site/index.html, the assets in html will be transformed to another path in dist/index.html like this:

<script src="\docs\89ee6b6452b6649c72b85a19637b8362.js"></script>

However, the \ separator is not a standard separator for web. With this fix, it will be transformed to:

<script src="/docs/89ee6b6452b6649c72b85a19637b8362.js"></script>

normalize-path is a wildly used module to normalize the path

[devongovett]

can you just use the builtin url.normalize for this instead of adding another dependency? https://nodejs.org/api/url.html#url_url_resolve_from_to

[brandon93s]

accidental close

It actually looks like url.resolve might not handle this correctly, either: repl.it.

normalize-path seems to only handle \\ and not \.

We may want to just roll our own utility for this...

[itsMapleLeaf]

Correct me if I'm wrong, but, as I understand it, the \ as it is in a JS string wouldn't ever show up in a path, right? Because \\ in JS means \, but there's no equivalent for \ since it's a special character, and not an output character. So url.resolve should work fine here

[xcatliu]

@brandon93s I tried normalize-path and url.resolve, both of them can handle this correctly. As @kingdaro said, \ is an escape symbol in JS string. So \\ means \ in string.

const url = require('url');

console.log(url.resolve('/base', 'path/to/resource'));
// will log /path/to/resource

console.log(url.resolve('/base/', 'path/to/resource'));
// will log /base/path/to/resource

console.log(url.resolve('\\base\\', 'path\\to\\resource'));
// will log /base/path/to/resource

console.log(url.resolve('\\path\\to\\resource', ''));
// will log /path/to/resource