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

• Vsevolod Goloviznin: If you are already sending a stringified array (why would you do that in the first place), why do you stringify it on the server again?
• Node.JS: Without stringify in NodeJS part I get exception. s1.postimg.org/v2urhx0kf/Capture.png
• Vsevolod Goloviznin: You need to use bodyparser middleware and just post the array without stringifying.
• Node.JS: @VsevolodGoloviznin Please Help man, I am stuck for days on this.
• harshes53: req.body could work, and remove over complexities of parsing and stringifying

Answer 1

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);
});

• dinigo: thankyou so much. I suspected it had something to do with the bodyParser. But wouldn't have found it in a week

Answer 2

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 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.