Converting a string into a JSON in JavaScript

Question

I have the following string:

[{"EventType":1,"ParticipantId":"1","X":123,"Y":123},{"EventType":2,"ParticipantId":"1","ParrentList":[123,124,125,126],"X":0,"Y":0}]

Could anybody give me an idea on how to convert this into a JSON structure and then get the value of each key, say:

EventType = 1;
ParticipantId = 1;
X = 123;
etc.

I'm actually trying to do it as follows, but I don't think that this is a smart way of doing that:

var results = [{"EventType":1,"ParticipantId":"1","X":123,"Y":123},{"EventType":2,"ParticipantId":"1","ParrentList":[123,124,125,126],"X":0,"Y":0}];  
  var arr = eval("(" + results + ')');

    for(var i=0;i<arr.length;i++){
        var obj = arr[i];
            for(var key in obj) {
            var attrName = key;
            var attrValue = obj[key];

              switch(attrName) {
               case "EventType" :
                   EventType = attrValue;
               break;
               case "ParticipantId" :
                   ParticipantId = attrValue;
               break;
               case "X" :
                   xCoord = attrValue;         
               break;
               case "Y" :
                   yCoord = attrValue;
                       break;

                 }
                    }
                  }

Thanks.

Answer 1

You already have a Javascript object. So you could just do:

for(var i = 0; i < results.length; i++) {
    var result = results[i];

    var eventType = result.EventType;
    var participantId = result.ParticipantId;
    var xCoord = result.X;
    var yCoord = result.Y;

    ...
}

There is no need to iterate over the properties and there is most certainly no reason to use eval in this case either. Javascript already recognizes your variable as an object.

Now if results was an actual string, I recommend using JSON.parse(...) to get back a Javascript object:

var results = JSON.parse(jsonString);

Answer 2

JSON.parse is your friend.

But yes... I am also confused. In your sample you already have JSON. You only need to parse it if you need to convert from a string to an object.

Answer 3

Could anybody give me an idea on how to convert this into a JSON structure and then get the value of each key

Point 1: this is a JSON structure. JSON is a notation for serialising data to transfer across the internet (or for other storage/transfer purposes, but this is the important one). JSON-encoded data is a string. Always. JSON notation strongly resembles (indeed, is entirely compatible with) the notation for objects in Javascript itself.

What you actually want to do is to convert a string of JSON-encoded data into a Javascript object. The relevant function is JSON.parse:

var data = JSON.parse(results);

You can then access the data in the normal way, e.g. data[0].EventType will be 1. I'm not sure what you mean by "get the value of each key", since the data is an array of similarly-structured objects, so there are multiple values for each key.