how to compare and replace values from one array to another in js?

Question

I have an array of objects, each object contains 2 properties, month & count. count has a default value of 0. I have a another array of object which I am pulling from a json file with different count values. I am trying to replace the count value from the 2nd array to the 1st.

eg

array1[
  { 
    month:1,
    count:0
  },
  { 
    month:2,
    count:0
  },
  { 
    month:3,
    count:0
  }
  { 
    month:4,
    count:0
  }
  etc...
]

array2[
  { 
    month:1,
    count:5
  },
  { 
    month:2,
    count:3
  },
  { 
    month:3,
    count:9
  }
  { 
    month:5,
    count:4
  }
  etc...
]

My problem is that my 2nd array is shorter as there are some months missing (due to no values for them in db) in this case I would like to skip and go to the next object. so the end result would look like this,

array1[
  { 
    month:1,
    count:5
  },
  { 
    month:2,
    count:3
  },
  { 
    month:3,
    count:9
  },
  { 
    month:4,
    count:0
  }
  { 
    month:5,
    count:4
  }
  etc...
]

my code so far

var array1 = [];

for (var i = 1; i <= 12; i++) {
  array1.push({
    month: i,
    count: 0
  })
}


$.getJSON(url, function (data) {
  for (var i = 0; i < data.length; i++) {
    if (array1[i].month == data[i].month) { //work until month 4
        array1[i].count = data[i].count 
    }
});

console.log(array1);

Nina Scholz · Accepted Answer · 2016-10-10 13:23:58Z

1

If you have always the months of a year in your array, then you can use the month as index for the original array and update if necessary.

for (var i = 0; i < data.length; i++) {
    array1[data[i].month - 1].count = data[i].count;
}

edited Oct 10, 2016 at 13:23

answered Oct 10, 2016 at 13:04

Nina Scholz

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Makarov Sergey · Accepted Answer · 2016-10-10 13:06:40Z

1

Result will be in the first array:

function mergeArrays(arr1, arr2) {
    arr1.forEach(function(item1) {
        var item2 = arr2.find(function (item2) {
            return item2.month === item1.month;
        });
        if (item2) {
            Object.assign(item1, item2);
        }
    })
}

answered Oct 10, 2016 at 13:06

Makarov Sergey

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