Save javascript variable to JSON file

Question

I'm wondering if it is possible to store data from variables to a json file ?

var json_object = {"test":"Hello"}
    $.ajax({
            url: "save.php",
            data: json_object,
            dataType: 'json',
            type: 'POST',
    success: function (json_object) {
        console.log(json_object);
        $("#data").text("Data has been saved.");},
    error: function (json_object){
        console.log(json_object);
        $("#data").text("Failed to save data !");}

This is what I use to save data, now instead of storing Hello as a string I would like Helloworld to be a variable for example

var hello = world;

You can do that, but it won't be JSON anymore. This also sounds a lot like an XY problem---what is it that you want to accomplish with this? — JJJ
– JJJ, Commented Oct 2, 2013 at 13:55
I'm creating a minigame in javascript and I thought I had to use json in order to save the data, how can I save that data instead then ? — Skugga
– Skugga, Commented Oct 2, 2013 at 13:57
Don't use global variables. Put all game data to an object and you can just pass that object around as-is. — JJJ
– JJJ, Commented Oct 2, 2013 at 14:01
I don't see anything wrong there, if you have a variable hello which contains an object, just check if "ajax.data" accepts objects, if not use JSON.stringify() to pass the data in, and JSON.parse() to read back to an an object. — bitoiu
– bitoiu, Commented Oct 2, 2013 at 14:28

siledh · Accepted Answer · 2013-10-02 14:29:56Z

First of all create a namespace for your game, e.g. Game:

var Game = {};

From now on, all variables that have to do with your game go there. This is to minimize the use of global scope (which is evil).

Then say you want to have a state with score and level. You do it like that:

Game.state = {
  score: 0,
  level: 1
}

During the game it can modified, e.g.:

Game.state.score = 42;
Game.state.level++;

To save it, send the Ajax request:

$.ajax({
        url: "save.php",
        data: {
            state: JSON.stringify(Game.state) // sending Game.state as JSON string
        },
        dataType: 'json',
        type: 'POST',
        success: function (json_object) {
            console.log(json_object);
            $("#data").text("Data has been saved.");
        },
        error: function (json_object) {
            console.log(json_object);
            $("#data").text("Failed to save data !");
        }
    }

JSON.stringify(Game.state) will be a string that looks like this: '{"level":0,"score":42}'.

Okay, so after the save you store the sent JSON object as String on your server or something and at some point in the future you want to retrieve it. You can achieve it by doing:

$.ajax({
        url: "load.php",
        data: "", // no data, we are just loading
        dataType: 'json',
        type: 'POST',
        success: function (state) {
            Game.state = state; // okay, state loaded and assigned to our Game.state!
        }
    }

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