JSON.parse返回字符串而不是对象 [英] JSON.parse returns string instead of object
问题描述
{"action":"login","args":["nosuccess"]}
在客户端上，我正在使用它来获取字符串:
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);
但是数据类型是字符串... 但是为什么呢?
evt.data返回:
"{\"action\":\"login\",\"args\":[\"nosuccess\"]}"
数据返回:
{"action":"login","args":["nosuccess"]}
WebSocket服务器是一个码头服务器，它通过Google用gson.toJson(class)Gson在json中解析的json中发送一个字符串和一个字符串数组.该类是一个包含String操作和String数组args的类.
websocket.js的完整源代码:
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));
}
如果我更改此行:
var data = JSON.parse(evt.data);
对此:
var data = JSON.parse("{\"action\":\"login\",\"args\":[\"nosuccess\"]}");
然后它是一个json对象，但是当我使用evt.data时，它是一个字符串. 如果我将行更改为此:
var data = JSON.parse(JSON.parse(evt.data));
然后它可以工作，但是为什么通常只用一个JSON.parse可以做到呢?
这似乎与 over 字符串化字符串相当一致.例如，我使用在控制台中呈现的\n和\r附带的FileReader.readAsText加载了一个文本文件，所以我做了-(JSON.stringify(reader.result)).replace(/(?:\\[rn])+/g, '')首先查看符号，然后删除它们.接受并在其上运行JSON.parse()会将其转换为非转义的字符串，因此再次运行JSON.parse()会创建一个对象.
如果不对字符串进行字符串化处理，它将转换为对象，通常没有必要，但是如果您无法控制所获得的值，则两次运行JSON.parse()都可以解决问题.
im writing a websocket client and i would like to receive messages as json strings. For this I need a login. And if the login isn't true i send a json string with nosuccess. JSON String:
{"action":"login","args":["nosuccess"]}
On the client I'm using this to get the string:
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 type of data is a string... But why?
evt.data returns:
"{\"action\":\"login\",\"args\":[\"nosuccess\"]}"
data returns:
{"action":"login","args":["nosuccess"]}
The WebSocket server is a jetty Server which sends a string and a string array in json parsed in json with gson.toJson(class) Gson by Google. The Class is a class containing String action and String array args.
Complete source code of 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);
to this:
var data = JSON.parse("{\"action\":\"login\",\"args\":[\"nosuccess\"]}");
Then it is a json object, but when I use evt.data then it is a string. If I change the line to this:
var data = JSON.parse(JSON.parse(evt.data));
Then it works, but why, normally it should do it with only one JSON.parse, should it?
This seems to be fairly consistent with over-stringified strings. For example I loaded a text file using FileReader.readAsText that came with \n and \r which rendered in the console, so I did - (JSON.stringify(reader.result)).replace(/(?:\\[rn])+/g, '') first to see the symbols, then to get rid of them. Taking that and running JSON.parse() on it converts it to a non-escaped string, so running JSON.parse() again creates an object.
If you do not stringify your string, it will convert to an object and often it is not necessary but if you have no control over the obtained value, then running JSON.parse() twice will do the trick.
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