方法说明：

将多个参数组合成一个 path （详细请看例子）

语法：

复制代码 代码如下:
path.join([path1], [path2], [...])

由于该方法属于path模块，使用前需要引入path模块（var path= require(“path”) ）

例子：

复制代码 代码如下:
path.join('/foo', 'bar', 'baz/asdf', 'quux', '..')
// returns
'/foo/bar/baz/asdf'
path.join('foo', {}, 'bar')
// throws exception
TypeError: Arguments to path.join must be strings

源码：

复制代码 代码如下:
// windows version
  exports.join = function() {
    function f(p) {
      if (!util.isString(p)) {
        throw new TypeError('Arguments to path.join must be strings');
      }
      return p;
    }
 
    var paths = Array.prototype.filter.call(arguments, f);
    var joined = paths.join('\\');
 
    // Make sure that the joined path doesn't start with two slashes, because
    // normalize() will mistake it for an UNC path then.
    //
    // This step is skipped when it is very clear that the user actually
    // intended to point at an UNC path. This is assumed when the first
    // non-empty string arguments starts with exactly two slashes followed by
    // at least one more non-slash character.
    //
    // Note that for normalize() to treat a path as an UNC path it needs to
    // have at least 2 components, so we don't filter for that here.
    // This means that the user can use join to construct UNC paths from
    // a server name and a share name; for example:
    // path.join('//server', 'share') -> '\\\\server\\share\')
    if (!/^[\\\/]{2}[^\\\/]/.test(paths[0])) {
      joined = joined.replace(/^[\\\/]{2,}/, '\\');
    }
 
    return exports.normalize(joined);
  };