《node入门》学习

node入门原书地址：https://www.nodebeginner.org/index-zh-cn.html

node入门，循序渐进讲了javascript，node的回调和一些api的应用，很清晰，翻译也很给力。最终是一个例子，可以上传图片以及展示。

最后例子，遇到了麻烦，运行报错

可见零时文件已经创建

代码如下

function upload(response, request){
    console.log("Request handler 'upload' was called.");
    
    var form = new formidable.IncomingForm();
    form.parse(request,function(error, fields, files){
        console.log("parsing done");
        console.log("F.U.P: "+files.upload.path);
        fs.renameSync(files.upload.path, "tmp/test.png");
        response.writeHead(200, {"Content-Type": "text/html"});
        response.write("received image:<br/>");
        response.write("<img src='/show' />");
        response.end();
    });
    
};

搜过以后发现是fs.renameSync()不能跨盘操作，且不会新建文件夹，所以重新指定路径“form.uploadDir = "tmp"”，然后在目录新建tmp文件夹，最后在show函数读取的路径做修改

修改后代码

function upload(response, request){
    console.log("Request handler 'upload' was called.");
    
    var form = new formidable.IncomingForm();
    form.uploadDir = "tmp";
    //console.log("about to parse");
    form.parse(request,function(error, fields, files){
        console.log("parsing done");
        console.log("F.U.P: "+files.upload.path);
        /**
        try{
            fs.renameSync(files.upload.path, "tmp/test.png");
        }catch(e){
            console.log(e);
        };
        
        fs.renameSync(files.upload.path, "tmp/test.png",function(error){
            if(error){
                fs.unlink("/tmp/test.png");
                fs.rename(files.upload.path,"/tmp/test.png");
            };
        });
        **/
        fs.renameSync(files.upload.path, "tmp/test.png");
        response.writeHead(200, {"Content-Type": "text/html"});
        response.write("received image:<br/>");
        response.write("<img src='/show' />");
        response.end();
    });
    
};

function show(response){
    console.log("Request handle 'show' was called.");
    fs.readFile("./tmp/test.png","binary",function(error,file){
        if(error){
            response.writeHead(500,{"Content-Type":"text/plain"});
            response.write(error + "
");
            response.end();
        }else{
            response.writeHead(200,{"Content-Type":"image/png"});
            response.write(file,"binary");
            response.end();
        };
    });
};

第五行及第35行有修改