Create new javascript array extracting data from object properties

Question

I need to convert a flat array where the similar data is held in separate properties into an array of arrays grouping the data fields from each property together. Hopefully an example will make sense of this.

The original array:

        [{"MtmDate":"2014-10-24", "MouldingID":"1233B", "ID":38, "Mtm01":5.10, "Mtm02":6.63,"Mtm03":5.84 },
         {"MtmDate":"2014-10-25", "MouldingID":"1233B", "ID":39, "Mtm01":5.13, "Mtm02":6.21,"Mtm03":6.64 },
         {"MtmDate":"2014-10-26", "MouldingID":"1233B", "ID":40, "Mtm01":5.68, "Mtm02":5.95,"Mtm03":6.37 },
...
]

Output required:

    [{"Mtm": 1, values: [{"MtmDate": "2014-10-24", "ID":38, data: 5.10},
                       {"MtmDate": "2014-10-25", "ID":39, data: 5.13},
                       {"MtmDate": "2014-10-26", "ID":40, data: 5.68}]},
     {"Mtm": 2, values: [{"MtmDate": "2014-10-24", "ID":38, data: 6.63},
                       {"MtmDate": "2014-10-25", "ID":39, data: 6.21},
                       {"MtmDate": "2014-10-26", "ID":40, data: 5.95}]},
     {"Mtm": 3, values: [{"MtmDate": "2014-10-24", "ID":38, data: 5.84},
                       {"MtmDate": "2014-10-25", "ID":39, data: 6.64},
                       {"MtmDate": "2014-10-26", "ID":40, data: 6.37}]},
     ]

I know that I can do this by 'manually' setting up objects for each data field and adding them to the new array:

    var mtm1 = { mtm: 1, values: [] }, mtm2 = { mtm: 2, values: [] }, mtm3 = { mtm: 3, values: [] };
    var dataByPoint = [];
    dataByPoint.push(mtm1);
    dataByPoint.push(mtm2);
    dataByPoint.push(mtm3);

and then iterating through the original array grabbing the data for each object:

$.each(d, function(index, value) {
    var details1 = { mtmDate: value.MtmDate, id: value.ID, data: value.Mtm01 };
    if (details1.data) dataByPoint[0].values.push(details1);

    var details2 = { mtmDate: value.MtmDate, id: value.ID, data: value.Mtm02 };
    if (details2.data) dataByPoint[1].values.push(details2);

    var details3 = { mtmDate: value.MtmDate, id: value.ID, data: value.Mtm03 };
    if (details3.data) dataByPoint[2].values.push(details3); 
});

However there are in fact a dozen of these data properties and this method seems long-winded. Is there a way I can populate the new array by looping through the data properties?

Mouser · Accepted Answer · 2015-02-23 16:56:18Z

var arr =[{"MtmDate":"2014-10-24", "MouldingID":"1233B", "ID":38, "Mtm01":5.10, "Mtm02":6.63,"Mtm03":5.84 },
         {"MtmDate":"2014-10-25", "MouldingID":"1233B", "ID":39, "Mtm01":5.13, "Mtm02":6.21,"Mtm03":6.64 },
         {"MtmDate":"2014-10-26", "MouldingID":"1233B", "ID":40, "Mtm01":5.68, "Mtm02":5.95,"Mtm03":6.37 }
		]
		
var newArr = [];		
	for (var i = 0; i < arr.length; i++)
        {
	    var obj = {};
	    obj.Mtm = (i+1);
	    obj.values = [];
        if (Object.keys(arr[i])[i+3]) //test if the `Mtm##` is present.
        {
              for (var c = 0; c < arr.length; c++)
              {
                   var keys = Object.keys(arr[c]);		
	       	   obj.values.push({"MtmDate" : arr[c].MtmDate, "ID" : arr[c].ID, "data" :  arr[c][keys[i+3]]}); 
	       }
        }
	    newArr.push(obj);
	}

document.write(JSON.stringify(newArr))

This should do it. It uses two loops to parse the data.

The outer loop creates the individual entries in the new array, while the inner loop parses all the entries from the original element, with the content split in the right way. Object.keys is used to select the correct data element based upon the looped index.

Jesús Quintana · Accepted Answer · 2015-02-23 16:27:57Z

1

Using the map function of array.

var originalArray =   [{"MtmDate":"2014-10-24", "MouldingID":"1233B", "ID":38, "Mtm01":5.10, "Mtm02":6.63,"Mtm03":5.84 },
         {"MtmDate":"2014-10-25", "MouldingID":"1233B", "ID":39, "Mtm01":5.13, "Mtm02":6.21,"Mtm03":6.64 },
         {"MtmDate":"2014-10-26", "MouldingID":"1233B", "ID":40, "Mtm01":5.68, "Mtm02":5.95,"Mtm03":6.37 },
...
]

var expectedArray = originalArray.map(function(v){
   return {mtm:v.ID, values:v}
})

answered Feb 23, 2015 at 16:27

Jesús Quintana

1,81313 silver badges18 bronze badges

4 Comments

a-d Over a year ago

v would be an object here OP needs an integer

Jesús Quintana Over a year ago

mmmm i look make a little change

Mouser Over a year ago

This will not create the array the OP wants. Mtm should be an index not the ID from the original array.

Howard Shaw Over a year ago

this isn't doing it - all the Mtm01's, 02's etc need to be grouped together

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