Parse Array of JSON objects in NodeJS

Question

I am wondering how can I parse Array of JSON objects in NodeJS?

I want to post JSON array to the server, and be able to use the received array as a regualar JavaScript array.

Thanks in advance.

This is my front-end part that I am converting Array to String using stringify function

document.getElementById("sendJson").addEventListener("click", function () {
    $.post("/echo", JSON.stringify(QuestionsArray), function (data) {
        alert(data);
    });
})

This my back-end part that I am trying to convert Array of JSON object to Array

app.post('/echo', function (req, res) {
    var Array = JSON.parse(JSON.stringify(req.toString()));
    res.end(Array[0]["QuestionText"].toString());
});

This is Array that I am trying to sent to the server:

[  
   {  
      "QuestionText":"What is your Name",
      "QuestionType":1
   },
   {  
      "QuestionText":"Where are you from",
      "QuestionType":2,
      "ChoiceList":[  
         "US",
         "UK"
      ]
   },
   {  
      "QuestionText":"Are you married",
      "QuestionType":3,
      "ChoiceList":[  
         "Yes",
         "No"
      ]
   }
]

Here is the source code

Answer 1

I'll try to explain this. First of all, you are crating a json string on the client.

JSON.stringify(QuestionsArray)

Then on the server, you are doing the same again:

JSON.stringify(req.toString()) // this is not needed

Then you parse the double stringifyed json string to a javascript object:

JSON.parse(JSON.stringify(req.toString()))

So now you actually have to parse it twice :). If you just stringify it on the server as you are now, and just call:

var arr = JSON.parse(req.toString());

You will get a javascript object that you can access like this:

res.end(arr[0].QuestionText.toString());

Have a look at this jsFiddle and open your developer tools. Look at the console when it runs and you will see where the problem is: example

Answer 2

In your app.js:

var bodyParser = require("body-parser");
...
app.use(bodyParser.urlencoded({extended: true}));

Then you can just use req.body to get the posted values:

app.post('/echo', function (req, res) {
    var Array = req.body.data;
    res.end(Array[0]["QuestionText"].toString());
});

In front-end, don't do any stringifying:

$.post("/echo", {data: QuestionsArray}, function (data) {
    alert(data);
});

Answer 3

You may actually send the JSON directly to server.

    $.ajax({
        url: "/echo",
        type: 'POST',
        data: JSON.stringify(QuestionsArray),
        processData: false,
        contentType: 'application/json'
    }).success(function (data) {
        alert(data);
    });

And in node.js, use bodyParser.json to get it back.

app.use(bodyParser.json({}));

app.post('/echo', function (req, res) {
    var array = req.body;
    res.end(array[0]["QuestionText"].toString());
});

By the way, do not use Array as variable name because Array represent the Array class used by JavaScript and your code has overwritten it.