思路:

1、callback 驱动

2、递归所有需要复制文件

3、在一定阀值下并发复制文件

4、运行需要安装 async.js ? ? npm install async

?

代码如下：

var async = require("async");
var fs = require("fs");
var path = require("path");
// cursively make dir 
function mkdirs(p, mode, f, made) {
	if (typeof mode === 'function' || mode === undefined) {
		f = mode;
		mode = 0777 & (~process.umask());
	}
	if (!made)
		made = null;

	var cb = f || function () {};
	if (typeof mode === 'string')
		mode = parseInt(mode, 8);
	p = path.resolve(p);

	fs.mkdir(p, mode, function (er) {
		if (!er) {
			made = made || p;
			return cb(null, made);
		}
		switch (er.code) {
		case 'ENOENT':
			mkdirs(path.dirname(p), mode, function (er, made) {
				if (er) {
					cb(er, made);
				} else {
					mkdirs(p, mode, cb, made);
				}
			});
			break;

			// In the case of any other error, just see if there's a dir
			// there already.  If so, then hooray!  If not, then something
			// is borked.
		default:
			fs.stat(p, function (er2, stat) {
				// if the stat fails, then that's super weird.
				// let the original error be the failure reason.
				if (er2 || !stat.isDirectory()) {
					cb(er, made);
				} else {
					cb(null, made)
				};
			});
			break;
		}
	});
}
// single file copy
function copyFile(file, toDir, cb) {
	async.waterfall([
			function (callback) {
				fs.exists(toDir, function (exists) {
					if (exists) {
						callback(null, false);
					} else {
						callback(null, true);
					}
				});
			}, function (need, callback) {
				if (need) {
					mkdirs(path.dirname(toDir), callback);
				} else {
					callback(null, true);
				}
			}, function (p, callback) {
				var reads = fs.createReadStream(file);
				var writes = fs.createWriteStream(path.join(path.dirname(toDir), path.basename(file)));
				reads.pipe(writes);
				//don't forget close the  when  all the data are read
				reads.on("end", function () {
					writes.end();
					callback(null);
				});
				reads.on("error", function (err) {
					console.log("error occur in reads");
					callback(true, err);
				});

			}
		], cb);

}

// cursively count the  files that need to be copied

function _ccoutTask(from, to, cbw) {
	async.waterfall([
			function (callback) {
				fs.stat(from, callback);
			},
			function (stats, callback) {
				if (stats.isFile()) {
					cbw.addFile(from, to);
					callback(null, []);
				} else if (stats.isDirectory()) {
					fs.readdir(from, callback);
				}
			},
			function (files, callback) {
				if (files.length) {
					for (var i = 0; i < files.length; i++) {
						_ccoutTask(path.join(from, files[i]), path.join(to, files[i]), cbw.increase());
					}
				}
				callback(null);
			}
		], cbw);

}
// wrap the callback before counting
function ccoutTask(from, to, cb) {
	var files = [];
	var count = 1;

	function wrapper(err) {
		count--;
		if (err || count <= 0) {
			cb(err, files)
		}
	}
	wrapper.increase = function () {
		count++;
		return wrapper;
	}
	wrapper.addFile = function (file, dir) {
		files.push({
			file : file,
			dir : dir
		});
	}

	_ccoutTask(from, to, wrapper);
}


function copyDir(from, to, cb) {
    if(!cb){
	  cb=function(){};
	}
	async.waterfall([
			function (callback) {
				fs.exists(from, function (exists) {
					if (exists) {
						callback(null, true);
					} else {
						console.log(from + " not exists");
						callback(true);
					}
				});
			},
			function (exists, callback) {
				fs.stat(from, callback);
			},
			function (stats, callback) {
				if (stats.isFile()) {
					// one file copy
					copyFile(from, to, function (err) {
						if (err) {
							// break the waterfall
							callback(true);
						} else {
							callback(null, []);
						}
					});
				} else if (stats.isDirectory()) {
					ccoutTask(from, to, callback);
				}
			},
			function (files, callback) {	
                // prevent reachin