特殊协议

WHATWG 网址标准认为少数网址协议方案在解析和序列化方式方面具有特殊性。 当使用这些特殊协议之一解析网址时，url.protocol 属性可能会更改为另一种特殊协议，但不能更改为非特殊协议，反之亦然。

例如，从 http 更改为 https 有效：

const u = new URL('http://example.org');
u.protocol = 'https';
console.log(u.href);
// https://example.org

但是，从 http 更改为假设的 fish 协议并不是因为新协议并不特殊。

const u = new URL('http://example.org');
u.protocol = 'fish';
console.log(u.href);
// http://example.org

同样，也不允许从非特殊协议更改为特殊协议：

const u = new URL('fish://example.org');
u.protocol = 'http';
console.log(u.href);
// fish://example.org

根据 WHATWG 网址标准，特殊协议方案有 ftp、file、http、https、ws 和 wss。

The WHATWG URL Standard considers a handful of URL protocol schemes to be special in terms of how they are parsed and serialized. When a URL is parsed using one of these special protocols, the url.protocol property may be changed to another special protocol but cannot be changed to a non-special protocol, and vice versa.

For instance, changing from http to https works:

const u = new URL('http://example.org');
u.protocol = 'https';
console.log(u.href);
// https://example.org

However, changing from http to a hypothetical fish protocol does not because the new protocol is not special.

const u = new URL('http://example.org');
u.protocol = 'fish';
console.log(u.href);
// http://example.org

Likewise, changing from a non-special protocol to a special protocol is also not permitted:

const u = new URL('fish://example.org');
u.protocol = 'http';
console.log(u.href);
// fish://example.org

According to the WHATWG URL Standard, special protocol schemes are ftp, file, http, https, ws, and wss.