Loop through an array of arrays containing object, and update the array in JavaScript/Angular

Question

I am trying to loop through an array of arrays with object [[{},{},{}],[{},{},{}]] , and create a new array that basically "totals" the arrays. I am a bit at a loss on how to achieve this.

My data looks like this:

[
  [{
    "2017-01-05": 607
  }, {
    "2017-01-06": 430
  }, {
    "2017-01-07": 357
  }, {
    "2017-01-08": 277
  }],
  [{
    "2017-01-09": 607
  }, {
    "2017-01-10": 430
  }, {
    "2017-01-11": 357
  }, {
    "2017-01-12": 277
  }]
],

I would like to "count" and "label" each week, and total each week. Example:

newArray: [{"Week 1": 1075}, {"Week 2": 1590}]

I know I should probably use a forEach loop, but then it gets a bit sketchy:

dateArray.forEach( function (arrayWeek)
{
  // push and name etc. functionality
});

I would greatly appreciate your assistance and guidance.

Answer 1

I would use the map function and reduce each week inside the map:

 var days = [ [{"2017-01-05":607}, {"2017-01-06":430}, {"2017-01-07":357}, {"2017-01-08":277}], [{"2017-01-09":607}, {"2017-01-10":430}, {"2017-01-11":357}, {"2017-01-12":277}] ]; function aggregator(memo, day) { for (var i in day) { memo += day[i]; } return memo; } // Original version from the question var weeks = days.map(function(week, index) { var obj = {}; obj['Week ' + (index + 1)] = week.reduce(aggregator, 0); return obj; }); console.log(weeks); // Follow up version from question in the comments var weeks2 = days.map(function(week, index) { return { name: 'week ' + (index + 1), total: week.reduce(aggregator, 0) }; }); console.log(weeks2); 

Answer 2

You can try something like this.

 var data=[[{"2017-01-05":607},{"2017-01-06":430},{"2017-01-07":357},{"2017-01-08":277}],[{"2017-01-09":407},{"2017-01-10":430},{"2017-01-11":357},{"2017-01-12":277}]]; var result = data.reduce(function(p, c, i) { var total = c.reduce(function(total, obj) { for (var k in obj) { total += obj[k]; } return total; }, 0); // Format object in any format you want var tmp = {}; tmp.name = "Week " + (i+1) tmp.total = total; // Push formatted object in array p.push(tmp) return p; }, []) console.log(result) 

Note, I'd suggest you to use an object instead of array of objects. Benefit of this would be that you will not require to loop over output to get value. You can directly so result['week'+index]

 var data=[[{"2017-01-05":607},{"2017-01-06":430},{"2017-01-07":357},{"2017-01-08":277}],[{"2017-01-09":407},{"2017-01-10":430},{"2017-01-11":357},{"2017-01-12":277}]]; var result = data.reduce(function(p, c, i) { var total = c.reduce(function(total, obj) { for (var k in obj) { total += obj[k]; } return total; }, 0); p["week" + (i + 1)] = total; return p; }, {}) console.log(result) 

Answer 3

the variable weeks should hold what you want... I'm assuming the week number is the actual week number in the year and not some index in the array. I'd also not use the same data structure but am adapting so that you won't need to change your structure.

var arr = [
    [{
        "2017-01-05": 607
    }, {
        "2017-01-06": 430
    }, {
        "2017-01-07": 357
    }, {
        "2017-01-08": 277
    }],
    [{
        "2017-01-09": 607
    }, {
        "2017-01-10": 430
    }, {
        "2017-01-11": 357
    }, {
        "2017-01-12": 277
    }]
]

function week(d) {
    // taken from http://stackoverflow.com/questions/6117814/get-week-of-year-in-javascript-like-in-php
    d.setHours(0, 0, 0, 0);
    d.setDate(d.getDate() + 4 - (d.getDay() || 7));
    return Math.ceil((((d - new Date(d.getFullYear(), 0, 1)) / 8.64e7) + 1) / 7);
}

var weeks = {};
for (var x in arr) {
    var subarr = arr[x]
    for (var y in subarr) {
        var obj = subarr[y];
        for (var when in obj) {
            var d = new Date(when);
            var which_week = "Week " + week(d);
            if (which_week in weeks) {
                weeks[which_week] += obj[when];
            } else {
                weeks[which_week] = obj[when];
            }
        }
    }
}

Answer 4

without forEach

var arrs = [
  [{
    "2017-01-05": 607
  }, {
    "2017-01-06": 430
  }, {
    "2017-01-07": 357
  }, {
    "2017-01-08": 277
  }],
  [{
    "2017-01-09": 607
  }, {
    "2017-01-10": 430
  }, {
    "2017-01-11": 357
  }, {
    "2017-01-12": 277
  }]
];

function loop1(arr, i, r){
    r = (r ? r : 0) + arr[i][Object.keys(arr[i])[0]];
    return ++i == arr.length ? r : loop1(arr, i, r);
}
function loop2(arrs, i, r){
    i = i ? i : 0;
    r = r ? r : {};
    r['Week ' + (i + 1)] = loop1(arrs[i], 0);
    return ++i == arrs.length ? r : loop2(arrs, i, r);
}

var newArr = loop2(arrs);