Sorting JSON array into multiple arrays

Question

I have the following json array

{"label":[{"name":"Government Schools",
          "datapoints":[{"year":"2007-2008","total":"1300"},
                        {"year":"2008-2009","total":"1280"},
                        {"year":"2009-2010","total":"1100"},
                        {"year":"2010-2011","total":"1400"}]
         },
         {"name":"Total Schools",
          "datapoints":[{"year":"2007-2008","total":"900"},
                        {"year":"2008-2009","total":"1000"},
                        {"year":"2009-2010","total":"1300"},
                        {"year":"2010-2011","total":"999"}]
         }]
}

I am trying to sort the datapoints into an array with the following format

var linedataline = [{dataPoints : [{ x: 1,
                                        y: 1300,
                                        label: "2007-2008"
                                    }, {
                                        x: 2,
                                        y: 1280,
                                        label: "2008-2009"
                                    }, {
                                        x: 3,
                                        y: 1100,
                                        label: "2009-2010"
                                    }, {
                                        x: 4,
                                        y: 1400,
                                        label: "2010-2011"
                                    }]
                                },
                                {dataPoints : [{ x: 1,
                                        y: 900,
                                        label: "2007-2008"
                                    }, {
                                        x: 2,
                                        y: 1000,
                                        label: "2008-2009"
                                    }, {
                                        x: 3,
                                        y: 1300,
                                        label: "2009-2010"
                                    }, {
                                        x: 4,
                                        y: 999,
                                        label: "2010-2011"
                                    }]

                            }];

I have used the following javascript

for(var i=0; i<data.label.length;i++){
                datapoints.length = 0;
                for(var j=0;j<data.label[i].datapoints.length;j++){
                    datapoints.push({
                                x: j+1,
                                y: data.label[i].datapoints[j].total,
                                label: data.label[i].datapoints[j].year
                    })
                }
                linedataline.push({ 
                        dataPoints: datapoints 
                })     
            }

where "data" is the parsed JSON. The problem is that linedataline does contain two arrays as required, but both print the second JSON array and not the first one. If I do not empty the datapoints array, it returns both the arrays but linedataline has array length = 8 and it does not separate the two arrays. What is the problem here?

That doesn't really have anything to do with sorting or JSON. You seem to want to convert an array of objects into a different format/structure. — Felix Kling
– Felix Kling, Commented Apr 14, 2014 at 6:23

ystan- · Accepted Answer · 2014-04-14 06:36:56Z

replace datapoints.length = 0; with var datapoints = [];

var data = {"label":[{"name":"Government Schools",
          "datapoints":[{"year":"2007-2008","total":"1300"},
                        {"year":"2008-2009","total":"1280"},
                        {"year":"2009-2010","total":"1100"},
                        {"year":"2010-2011","total":"1400"}]
         },
         {"name":"Total Schools",
          "datapoints":[{"year":"2007-2008","total":"900"},
                        {"year":"2008-2009","total":"1000"},
                        {"year":"2009-2010","total":"1300"},
                        {"year":"2010-2011","total":"999"}]
         }]
};
var linedataline = [];
for(var i=0; i<data.label.length;i++){
                var datapoints = [];
                for(var j=0;j<data.label[i].datapoints.length;j++){
                    datapoints.push({
                                x: j+1,
                                y: data.label[i].datapoints[j].total,
                                label: data.label[i].datapoints[j].year
                    });
                }
                linedataline.push({ 
                        dataPoints: datapoints 
                });
            }

emn178 · Accepted Answer · 2014-04-14 06:29:40Z

1

You should create new instance.

for(var i=0; i<data.label.length;i++){
  var datapoints = [];
  ...
}

answered Apr 14, 2014 at 6:29

emn178

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3 Comments

P Kero Over a year ago

Yes I have it created. Havent mentioned it in the code here. I have created all the instances.

emn178 Over a year ago

But you miss to create new instance for each datapoints in the loop.

P Kero Over a year ago

Oh, I had all the arrays created outside the loops. I hadn't created an instance inside the loop. This seems to work. Thank you so much!

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