Filter unique array values and sum values

Question

I have the following js array:

for(var j = 0; j < array.length; j++){
  arr.push([array[j][0],array[j][1],array[j][2]]);
}

And it translates into this:

Number, type, qty

[[12345, "product", "10"],[12345, "product", "15"],[1234567, "other", "10"]]

What I've been trying to do is to filter the unique product number array[j][0] and sum the qty array[j][2] if there's more than one and I was able to do the unique filter by doing the following:

for(var o = 0; o < arr.length; o++){
  if (!n[arr[o][1]]){
     n[arr[o][1]] = true
     r.push(arr[o]);
  }
}

I would like your help to figure this out.. What I'm expecting to achieve is something like this:

[[12345, "product", "25"],[1234567, "other", "10"]]

Since product 12345 was repeated I only need to display it once and sum the qty of the other products with the same product number.

Yes, filtering out the unique numbers and adding up the totals @DaveNewton — CCastillo
– CCastillo, Commented Mar 10, 2016 at 22:40
(That was hint: use the hash to track IDs, when you iterate over an item with an existing array, do math; when you find an ID w/o a value, create the new entry with the price.) — Dave Newton
– Dave Newton, Commented Mar 10, 2016 at 22:43
Have you considered moving this piece of business logic to the back end? In a production system, it's going to be much easier and more efficient to write queries to achieve what you want. — Nicholas Byfleet
– Nicholas Byfleet, Commented Mar 10, 2016 at 22:43
@NicholasByfleet My guess is that this is an assignment, so it would not matter. — Adam Buchanan Smith
– Adam Buchanan Smith, Commented Mar 10, 2016 at 22:44

George Marcus · Accepted Answer · 2016-03-10 22:53:14Z

3

var productIndex = {};
var result = [];
for (var i = 0; i < arr.length; i++) {
  var productId = arr[i][0];
  if (productIndex[productId] === undefined) {
    productIndex[productId] = result.length;
    result.push(arr[i]);
  } else {
    var index = productIndex[productId];
    result[index][2] = String(+result[index][2] + +arr[i][2]);
  }
}

answered Mar 10, 2016 at 22:53

George Marcus

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3 Comments

CCastillo Over a year ago

I can see where you are going with this, it makes sense. I haven't been able to make it work though

George Marcus Over a year ago

What are you having trouble with? It works for your sample array.

CCastillo Over a year ago

My mistake was replacing === with == This works!! Thanks

Chris · Accepted Answer · 2016-03-10 22:53:28Z

I am sure there are better ways. But I just changed it to an object, added them and changed it back to an array. Here you go:

https://jsfiddle.net/ct6to1Lv/

var a = [[12345, "product", "10"],[12345, "product", "15"],[1234567, "other", "10"]];
var b = {};
var c = [];

for(var i = 0; i < a.length; i++) {
    if(!b.hasOwnProperty(a[i][0])) {
    b[a[i][0]] = {};
    b[a[i][0]]['qty'] = 0;
  }
  b[a[i][0]]['id'] = a[i][0];
  b[a[i][0]]['name'] = a[i][1];
    b[a[i][0]]['qty'] += parseInt(a[i][2]);
}

for(key in b) {
    c[c.length] = [b[key]['id'], b[key]['name'], b[key]['qty']];
}

$(function(){
$('#console').append(a.toString()+'<br />');
$('#console').append(JSON.stringify(b)+'<br />');
$('#console').append(c.toString());
});

isvforall · Accepted Answer · 2016-03-10 23:00:49Z

0

var arr = [[12345, "product", "10"],[12345, "product", "15"],[1234567, "other", "10"]];

var obj = {};

arr.forEach(function(e){
    var t = e[0];
    if(obj[t]) {
        obj[t][2] += +e[2];
    } else {
        t = [];
        t[0] = e[0];
        t[1] = e[1];
        t[2] = +e[2];
        obj[e[0]] = t;
    }
});

var res = [];

Object.keys(obj).forEach(function(k) {
    res.push(obj[k]);
});

console.log(res);

Result:

[ [ 12345, 'product', 25 ], [ 1234567, 'other', 10 ] ]

answered Mar 10, 2016 at 23:00

isvforall

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Comments

Nina Scholz · Accepted Answer · 2016-03-11 14:03:26Z

0

To complete the possibillities, here a solution with a temporary object, which is hidden in this.

var data = [[12345, "product", "10"], [12345, "product", "15"], [1234567, "other", "10"]],
    result = function (data) {
        var r = [];
        data.forEach(function (a) {
            if (!this[a[0]]) {
                this[a[0]] = [a[0], a[1], 0];
                r.push(this[a[0]]);
            }
            this[a[0]][2] += +a[2];
        }, {});
        return r;
    }(data);

document.write('<pre>' + JSON.stringify(result, 0, 4) + '</pre>');

answered Mar 11, 2016 at 14:03

Nina Scholz

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Comments

jherax · Accepted Answer · 2016-03-11 16:09:36Z

The reduce() method applies a function against an accumulator and each value of the array (from left-to-right) to reduce it to a single value.

See Array.prototype.reduce() and Array.prototype.sort()

var list = [[12345, "product", "10"], [12345, "product", "15"], [1234567, "other", "10"], [12345, "product", "5"]];

//first we sort the array by id
//@pv = previous value; @cv = current value
list.sort(function(pv, cv) {
    var a = +pv[0],
        b = +cv[0];
    return a - b;
});

//reduce the array for repeated elements
//@pv = previous value; @cv = current value
var reduced = list.reduce(function (pv, cv) {
    //slice keeps reference when element is an object/array
    var last = pv.slice(-1)[0];
    if (last === undefined) return [cv];
    //compares the id
    if (last[0] == cv[0]) 
        last[2] = +last[2] + (+cv[2]); //sums values
    else pv.push(cv); //order elements
    return pv;
}, []); //[] initial value for @pv

console.log(reduced);

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