Trying to simple PUT request to JSON file in Node.js

Question

Im trying to create a PUT method to update a obj.json file and display its contents after its been uploaded. I get an empty object and no contents?

 function upload(response, request) {
    console.log("Request handler 'upload' was called.");

    var form = new formidable.IncomingForm();
    console.log("about to parse");

    form.parse(request, function(error, fields, files){
        response.writeHead(200, {'content-type': 'application/json'});
        response.write('received upload:\n\n');
        response.end(util.inspect({fields: fields, files: files}));
    });

    form.on('file', function(field, file) {
        console.log(file);
        if (file.type == 'application/json') {
            jsonObject = JSON.parse(fs.readFileSync(file.path, 'utf8'));
            console.log(jsonObject);
        } else { console.log('wrong file');}
    });
}

function update(response, request) {
    console.log("Request handler 'update' was called.");
    response.writeHead(200, {"Content-Type": "application/json"});

    var form = new formidable.IncomingForm();
    console.log("about to parse");

    form.parse(request, function(error, fields, files){
        response.writeHead(200, {'content-type': 'application/json'});
        response.write('ready to update:\n\n');
        response.end(util.inspect({fields: fields, files: files}));
    });

    form.on('file', function(field, file) {
        console.log(file);
        if (file.type == 'application/json') {
            JSON.parse(fs.writeFileSync(file.path, JSON.stringify('"test":"Okay"'), 'utf8'));
            console.log(jsonObject);
        } else { console.log('wrong file');}
    });

}

I was able to upload the file and access the json but I can't change the contents of the file now. Any thoughts on how to do that? Also, would delete method be the same?

sctskw · Accepted Answer · 2015-02-16 22:05:34Z

1

You asked 2 questions here, hence I am giving you 2 separate answers. Updating a JSON file is like anything else:

var fs = require('fs');
var filename = '/tmp/content.json';
var file = fs.readFileSync(filename);
var json = JSON.parse(file);

//update the object
json.newValue = 'testValue';

//update the file with new object
fs.writeFileSync(filename, JSON.stringify(json));

answered Feb 16, 2015 at 22:05

sctskw

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7 Comments

sctskw Over a year ago

the idea here is you are overwriting the file with an entirely new object that contains your updates. You can't tell the file to only update a portion of it. If you only stringify the update, then you'll be erasing the original contents.

rahul2001 Over a year ago

Thanks! However, the filename is hardcoded in -- I am trying to access the same file that was uploaded in the original GET request. Is there a way to access the filename from the upload?

rahul2001 Over a year ago

Also, when '/update' is routed it shows up as a POST request and not a PUT. '/' and '/upload' and '/show' are GET, POST, GET respectively. Any idea why '/update' is not a PUT. Thats for your help, im a newb to backend dev.

sctskw Over a year ago

from the code above, the filename does not appear to be hardcoded. you can access it via file.path which you're already doing.

sctskw Over a year ago

I don't have enough code to answer your question regarding the PUT. If you're using express as your application routing, it's as simple as router.put('/update', update); , but without me being able to see your routing code, I cannot answer that.

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sctskw · Accepted Answer · 2015-02-16 22:02:21Z

0

https://www.npmjs.com/package/multer

This is a great library for file upload abilities. When you perform a file POST, it must be submitted with Content-type: 'multipart/form-data'. Then you can access the JSON file like so:

req.files.<nameOfFileInput>

I've never used formidable, but I assume it works in the same way, and it may even use multer behind the scenes. My guess would be your form does not have enctype="multipart/form-data" set which is why your files aren't being sent to the server.

answered Feb 16, 2015 at 22:02

sctskw

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