JSON.parse returns a string instead of an object

Question

im writing websocket client, and I would like to receive messages as json strings. To do this, I need a login. And if the login is incorrect, I am sending a json string with nosuccess. JSON String:

{"action":"login","args":["nosuccess"]} 

On the client, I use this to get the line:

 WebSocket socket = new WebSocket("ws://localhost:2555/api"); socket.onmessage = function(evt) { console.log(evt.data); console.log(typeof(evt.data)); onMessage(evt); } function onMessage(evt) { var data = JSON.parse(evt.data); var action = data.action; var args = data.args; console.log(data); console.log(typeof(data)); console.log(action); console.log(args); 

But the data type is a string ... But why?

evt.data returns:

  "{\"action\":\"login\",\"args\":[\"nosuccess\"]}" 

:

  {"action":"login","args":["nosuccess"]} 

A WebSocket server is a berth server that sends a string and a string array to json processed by json using gson.toJson (class) Gson from Google. A class is a class that contains the String action and args of the String array.

Full source code websocket.js:

 var socket; function openWebsocket(adress) { socket = new WebSocket(adress); socket.onopen = function(evt) { console.log("Socket opened [" + adress + "]"); }; socket.onclose = function(evt) { loadPage("login.html"); console.log("Socket closed [" + evt.code + "]"); } socket.onmessage = function(evt) { onMessage(evt); } socket.onerror = function(evt) { console.log("Socket couldn't connect [" + evt.message + "]"); showMessage("fa-exclamation-circle", "Socket couldn't be established!", 1000); } } function onMessage(evt) { var data = JSON.parse(evt.data); var action = data.action; var args = data.args; console.log(data); console.log(typeof(data)); console.log(action); console.log(args); $(".card-container h3").html(data); if(action == "login") { if(args[0] == "success") { loadPage("dashboard.htm"); currentpage = "dashboard.htm"; showMessage("fa-check", "Du wurdest erfolgreich eingeloggt", 2000); } else if(args[0] == "nosuccess") { loadPage("login.html"); currentpage = "login.html"; showMessage("fa-exclamation-circle", "Falscher Benutzername oder falsches Passwort", 2000); } else if(args[0] == "unauthenticated") { loadPage("login.html"); currentpage = "login.html"; showMessage("fa-exclamation-circle", "Login failure: not authenticated", 2000); } } } function sendMessage(json) { $(".card-container h3").html(JSON.stringify(json)); console.log(JSON.stringify(json)); socket.send(JSON.stringify(json)); } 

If I change this line:

  var data = JSON.parse(evt.data); 

:

 var data = JSON.parse("{\"action\":\"login\",\"args\":[\"nosuccess\"]}"); 

Then it is a json object, but when I use evt.data it is a string. If I changed the line to this:

  var data = JSON.parse(JSON.parse(evt.data)); 

Then it works, but why, as a rule, it should do it with only one JSON.parse, right?

Answer 1

As noted in the comments, this issue has been resolved. If you get a response from the server as a "gated object", you can turn it into a regular object with JSON.parse () as follows:

 var stringResponse = '{"action":"login","args":["nosuccess"]}'; var objResponse = JSON.parse(stringResponse); console.log(objResponse.args); 

You can also try the above code here .

As for why the server returns the string when you really need the object, it really comes down to your internal code, which library you use, and the transport protocol. If you just want your front-end code to work, use JSON.parse. If you want to edit the reaction of the backend, please provide additional information.