url 包提供了三个方法
假设url字符串为：'http://user:pass@host.com:8080/p/a/t/h?query=string#hash'
一、url.parse(urlStr, [parseQueryString], [slashesDenoteHost]）
按url规则拆解urlStr字符串，接收三个参数
- urlStr， url字符串(必传)
- parseQueryString， bool类型， 默认值false。 对url中query部分解析后输出格式的选择， true的话输出格式由默认的 'query=string' 转为对象格式{ query: 'string' }
- slashesDenoteHost, bool类型， 默认值false。
parse解析获取的对象的结构，这个对认识url的组成也是极好的：
href: The full URL that was originally parsed. Both the protocol and host are lowercased.
Example: 'http://user:pass@host.com:8080/p/a/t/h?query=string#hash'
protocol: The request protocol, lowercased.
Example: 'http:'
slashes: The protocol requires slashes after the colon
Example: true or false
host: The full lowercased host portion of the URL, including port information.
Example: 'host.com:8080'
auth: The authentication information portion of a URL.
Example: 'user:pass'
hostname: Just the lowercased hostname portion of the host.
Example: 'host.com'
port: The port number portion of the host.
Example: '8080'
pathname: The path section of the URL, that comes after the host and before the query, including the initial slash if present.
Example: '/p/a/t/h'
search: The 'query string' portion of the URL, including the leading question mark.
Example: '?query=string'
path: Concatenation of pathname and search.
Example: '/p/a/t/h?query=string'
query: Either the 'params' portion of the query string, or a querystring-parsed object.
Example: 'query=string' or {'query':'string'}
hash: The 'fragment' portion of the URL including the pound-sign.
Example: '#hash'
二、 url.format(urlObj)
parse的反用，将对象解析成url字符串
三、 url.resolve(from, to)
为URL或 href 插入 或 替换原有的标签
var url = require('url');
var a = url.resolve('/one/two/three', 'four') ,
b = url.resolve('http://example.com/', '/one'),
c = url.resolve('http://example.com/one', '/two');
console.log(a +","+ b +","+ c);
//输出结果：
///one/two/four
//http://example.com/one
//http://example.com/two
