URL 编码分两种：整条 URL 编码（encodeURI，保留 : / ? 等结构符号）和参数值编码（encodeURIComponent，全部特殊字符都编码）——选错就会出 bug，这里分开给。再往下还能把一条 URL 拆开看：协议、主机、端口、路径、每个查询参数，清清楚楚。URL encoding comes in two flavors: full-URL encoding (encodeURI, keeps structural characters like : / ?) and component encoding (encodeURIComponent, encodes everything) — picking the wrong one is a classic bug, so both are here. Below, any URL is broken down into protocol, host, port, path and every query parameter.
解码时 + 号会按查询参数的惯例转成空格（application/x-www-form-urlencoded 规则）；如果你的 + 是字面加号，请注意区分。中文等非 ASCII 字符编码为 UTF-8 百分号编码，与浏览器地址栏行为一致。On decode, + is turned into a space following the query-string convention (application/x-www-form-urlencoded). Non-ASCII characters are percent-encoded as UTF-8, exactly as browsers do.