如何用代码说明Node.Js文件处理模块

//文件处理类
var fs = require('fs');
var path = require('path');
var util = require('util');
var File = {
    in : function(content,flag){
        this.writeToFile("app.log",content,flag);
    },
    on : function(content,flag){
        this.appendToFile("app.log",content,flag);
    },
    writeInFile : function(content,flag){
        this.writeToFile("app.log",content,flag);
    },
    writeToFile : function(sourceFile,content,flag){
        fs.writeFileSync(sourceFile,util.format(content));
        if(flag){
            console.log("内容写入成功");
        }
    },
    appendToFile : function(sourceFile,content,flag){
        fs.appendFileSync(sourceFile,"\n\n***************    " +this.getTime()+"   **************\n\n");
        fs.appendFileSync(sourceFile,util.format(content));
        if(flag){
            console.log("内容追加成功");
        }
    },
    //复制文件
    copyFile : function(sourceFile,targetFile,log){
        File.makeDirs(path.dirname(targetFile),function(){
            fs.writeFileSync(targetFile,fs.readFileSync(sourceFile));
            if(log){
                  console.log(sourceFile + '->' + targetFile + '复制成功');
              }
        });
    },
    //文件复制到目录
    copyFileToDir :function(sourceFile,targetDir,targetName,log){
        //获取文件名
        var name = '';
        if(targetName != undefined){
            var sourceExt = path.extname(sourceFile);
            var targetExt = path.extname(targetName);
            //得到后缀一样的文件
            name = path.basename(targetName,targetExt) + sourceExt;
        }
        else{
            name = path.basename(sourceFile);
        }
        this.makeDirs(targetDir,function(){
            File.copyFile(sourceFile,path.join(targetDir,name),log);
        });
    },
    //目录复制
    copyDir : function(sourceDir,targetDir,log){
        var sourceDirFiles = this.getDirs(sourceDir);
        sourceDirFiles.forEach(function(item){
            //获取相对路径
            var relativePath = path.relative(sourceDir,item);
            var targetAbsolutePath = path.join(targetDir,relativePath);
            File.copyFile(item,targetAbsolutePath,log);
        });
        console.log("done");
    },
    makeDirs : function(filepath,callback){
        fs.exists(filepath,function(exists){
            if(exists){
                callback();
            }
            else{
                File.makeDirs(path.dirname(filepath),function(){
                    fs.mkdir(filepath,callback);
                });
            }
        });
    },
    getDirs : function(dirpath,result){
        if(result == undefined){
            result = [];
        }
        var dirList = fs.readdirSync(dirpath);
        dirList.forEach(function(item){
            var cfile = path.join(dirpath,item);
            if(fs.statSync(cfile).isDirectory()){
                  File.getDirs(cfile,result);
            }else{
                  result.push(cfile);
            }
        });
        return result;
    },
    getTime:function (d){
        d = d || new Date();
        return d.getHours() + ":" + this.getTwo(d.getMinutes()) + ":" + this.getTwo(d.getSeconds());
    },
    getTwo:function(m){
        return m < 10 ? ("0" + m) : m;
    }
}
 
 
module.exports = File;