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How to use javascript to loop through key, values ​​and add one key value when another match

I have a dataset of records that looks like this:

[{
 "d1d":"2015-05-28T00:00:00.000Z",
 "d1h":0,
 "d15m":0,
 "ct":3
},
{
 "d1d":"2015-05-28T00:00:00.000Z",
 "d1h":0,
 "d15m":0,
 "ct":1
}
]

The ct value changes with every record. If d1d, d1h and d15m are the same in one or more records, then I need to merge those records into one with the sum of all ct values.

I have jquery, can I use grep for this?

I understand that the server side can improve my data handling, but I have no control over that.

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2 answers


You don't need to use jQuery for this, vanilla JavaScript will do. I will show you two solutions to your problem:

Example 1: Violating Array # reduce as an iterator

var intermediaryArray = [];
dataset.reduce(function(prev, curr) {
  if(prev.d1d === curr.d1d && prev.d1h === curr.d1h && prev.d15m === curr.d15m) {
    intermediaryArray.push({
      d1d: prev.d1d,
      d1h: prev.d1h,
      d15m: prev.d15m,
      ct: prev.ct + curr.ct
    });
  } else {
    // push the one that wasn't the same
    intermediaryArray.push(curr);
  }
  // return current element so reduce has something to work on
  // for the next iteration.
  return curr;
});

Example 2: Using Array # Map and Array # Shorten Together



This example uses underscore.js to demonstrate the logic of what you want to do.

.map()

creates a new array of grouped objects. .groupBy()

creates an array of subarrays containing objects that pass a predicate that all objects must have the same function d1d

or grouping. .reduce()

boils all subarrays down to one value, your object being appended to ct

each other.

var merged = _.map(_.groupBy(a, 'd1d'), function(subGroup) {
  return subGroup.reduce(function(prev, curr) {
    return {
      d1d: prev.d1d,
      d1h: prev.d1h,
      d15m: prev.d15m,
      ct: prev.ct + curr.ct
    };
  });
});
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Here's one possible solution:

var dataset = [{
 "d1d":"2015-05-28T00:00:00.000Z",
 "d1h":0,
 "d15m":0,
 "ct":3
},
{
 "d1d":"2015-05-28T00:00:00.000Z",
 "d1h":0,
 "d15m":0,
 "ct":1
}
]

function addCt(dataset) {
  var ctMap = {}
  var d1d, d1h, d15m, ct, key, value
  for (var ii=0, record; record=dataset[ii]; ii++) {
    key = record.d1d+"|"+record.d1h+"|"+record.d15m
    value = ctMap[key]
    if (!value) {
      value = 0
    }
    value += record.ct
    ctMap[key] = value
  }

  return ctMap
}

ctMap = addCt(dataset)
console.log(ctMap)
// { "2015-05-28T00:00:00.000Z|0|0": 4 }


You might want to build the key in a different way. You can set a value for an object containing d1d, d1h, d15m and cumulated ct values, with one object for all corresponding d1d, d1h, and d15m values.

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