解析 JSON 中的对象，并检索数据

Question

So I have a variable name "userList".

This variable is a JSON containing a few objects, depending on the amount of users online...

Here is the JSON/variable stringifed: (Contains two users.)

{
  "User1": {
    "ident": "guest#1",
    "username": "Guest1",
    "posx": 2,
    "posy": 10,
    "lineWidth": "1",
    "lineColor": "00baff"
  },
  "User2": {
    "ident": "guest#2",
    "username": "Guest 2",
    "posx": 1,
    "posy": 5,
    "lineWidth": "1",
    "lineColor": "000000"
  }
}

How could I log every objects "username" value? Here's my script:

if (obj.msg === "/log") { //If EventSource's obj.msg ='s ...
  var list = JSON.stringify(userList) //String the variable.
  console.log(list) // Log the objects.
} else {
  console.log("Event msg is not /log ")
}

I've tried doing this:

console.log(list.username)

Answer 1

You can loop through the object's keys and access the username fields like this:

 var list = { "8micxp7q5w5tfsrkkw9iys7l2ead7tls": { "ident": "8micxp7q5w5tfsrkkw9iys7l2ead7tls", "username": "Antidote", "posx": 1002, "posy": 125, "lineWidth": "1", "lineColor": "00baff", "ignore": false, "status": "w" }, "1fjw6u6ok8q6jrqcnr47yymbaida2iwp": { "ident": "1fjw6u6ok8q6jrqcnr47yymbaida2iwp", "username": "from Lehi, United States", "posx": 989, "posy": 124, "lineWidth": "1", "lineColor": "000000", "ignore": false, "status": "w" } } for (item in list) { console.log(list[item]['username']) }

Answer 2

You have a map of two objects, you can only access them using their key. Also, JSON.stringify returns a string. To parse a string to from a JSON object, use JSON.parse.

if (obj.msg === "/log") { //If EventSource's obj.msg ='s ...
  var list = JSON.parse(JSON.stringify(userList)) // this is not needed your userList is already parsed
  
  // First Approach es5
  for(var key in list){
    console.log(list[key].username); // here is how u can access your name
  }

  // Second Approach es6
  for (const item of list){
    console.log(item.username);
  }
} else {
  console.log("Event msg is not /log ")
}

Answer 3

Your console.log() statement doesn't reference the key despite referencing the value, so it would make more sense to do:

console.log(list["8micxp7q5w5tfsrkkw9iys7l2ead7tls"].username);

If you aim to get the username values of the keys of the objects manually/individually rather than iterating through the username instances in the object's keys, you could also use the JSON.parse() method as follows. Make sure your JSON list is a string:

var list = '{ "pmicxp7q5w5tfsrkkw9iys7l2ead7tls": { "ident": "8micxp7q5w5tfsrkkw9iys7l2ead7tls", 
   "username": "Antidote", "posx": 1002, "posy": 125, "lineWidth": "1", "lineColor": "00baff", 
   "ignore": false, "status": "w"}, "1fjw6u6ok8q6jrqcnr47yymbaida2iwp": { "ident": 
   "1fjw6u6ok8q6jrqcnr47yymbaida2iwp", "username": "from Lehi, United States", "posx": 989, 
   "posy": 124, "lineWidth": "1", "lineColor": "000000", "ignore": false, "status": "w"}}';

var obj = JSON.parse(list);
var username1 = obj["8micxp7q5w5tfsrkkw9iys7l2ead7tls"].username;   // or obj.8micxp7q5w5tfsrkkw9iys7l2ead7tls.username
var username2 = obj["1fjw6u6ok8q6jrqcnr47yymbaida2iwp"].username;   // or obj.1fjw6u6ok8q6jrqcnr47yymbaida2iwp.username

Answer 4

To show all the users usernames at once, you can use Object.values(userList) to get an array of the objects inside userList object then use forEach method to loop through that new array :

 const userList = { "8micxp7q5w5tfsrkkw9iys7l2ead7tls": { "ident": "8micxp7q5w5tfsrkkw9iys7l2ead7tls", "username": "Antidote", "posx": 1002, "posy": 125, "lineWidth": "1", "lineColor": "00baff", "ignore": false, "status": "w" }, "1fjw6u6ok8q6jrqcnr47yymbaida2iwp": { "ident": "1fjw6u6ok8q6jrqcnr47yymbaida2iwp", "username": "from Lehi, United States", "posx": 989, "posy": 124, "lineWidth": "1", "lineColor": "000000", "ignore": false, "status": "w" } } Object.values(userList).forEach(i => console.log(i.username));

But if you need to get the username from a certain object in userList , you'll need to access that object using it name (key) :

 const userList = { "8micxp7q5w5tfsrkkw9iys7l2ead7tls": { "ident": "8micxp7q5w5tfsrkkw9iys7l2ead7tls", "username": "Antidote", "posx": 1002, "posy": 125, "lineWidth": "1", "lineColor": "00baff", "ignore": false, "status": "w" }, "1fjw6u6ok8q6jrqcnr47yymbaida2iwp": { "ident": "1fjw6u6ok8q6jrqcnr47yymbaida2iwp", "username": "from Lehi, United States", "posx": 989, "posy": 124, "lineWidth": "1", "lineColor": "000000", "ignore": false, "status": "w" } } console.log(userList['8micxp7q5w5tfsrkkw9iys7l2ead7tls'].username); /** output: Antidote **/ console.log(userList['1fjw6u6ok8q6jrqcnr47yymbaida2iwp'].username); /** output: from Lehi, United States **/

Answer 5

You know that username is not an attribute of the userList object, so you need to iterate over the Object in order to access each user object:

for (var ident in userList) {
    if (userList.hasOwnProperty(ident)) {
        console.log(userList[ident].username);
    }
}

Also, are you trying access attributes of the String list ? If you want to access the attributes programmatically you should keep the Object as userList , because once you call JSON.stringify(userList) , you'll get a pretty useless String representation of the Object .