JS: Ordered iteration of object

Question

There is an object like this...

{
  2016: {
    3 : [
      { field: "content 1" }
      { field: "content 2" }
    ]
    10 : [
      { field: "content 3" }
    ]
  }
  2017: {
    8 : [
      { field: "content 4" }
    ]
  }
}

...and I need to get access to the subelements in an ascending order. That means I want to process 2016 object first, then 2017 object.

Within that I need to process the month objects also in ascending order.

Iteration like...

for (var year in map) {
    if (map.hasOwnProperty(year)) {
        console.log(year)
    }
}

won't do the job properly.

There is no order in objects, you'd have to create your own map and follow that. — adeneo
– adeneo, Commented Jul 28, 2017 at 18:19
javascript can't sort maps sorry, you're going to have to do something like adding an extra property in you objects like 2016: {year: 2016, ...} then convert the map into an array then sort the array by years — David Villarreal
– David Villarreal, Commented Jul 28, 2017 at 18:21

Ori Drori · Accepted Answer · 2017-07-28 18:45:48Z

2

To get an ordered array of the content, recursively iterate the object, while getting the data by sorted keys, and using Array#concat to flatten the array.

var data = {"2016":{"3":[{"field":"content 1"},{"field":"content 2"}],"10":[{"field":"content 3"}]},"2017":{"8":[{"field":"content 4"}]}};

function iterateByOrder(data) {
  var sorterKeys = Object.keys(data).sort(function(a, b) {
    return a - b; // sort by converting the keys to numbers
  });
  
  return [].concat.apply([], sorterKeys.map(function(key) { // mapping the propeties to values, and flatting sub arrays
    return typeof data[key] === 'object' ? iterateByOrder(data[key]) : data[key];
  }));
}

var result = iterateByOrder(data);

console.log(result);

edited Jul 28, 2017 at 18:45

answered Jul 28, 2017 at 18:25

Ori Drori

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Comments

score 2 · Accepted Answer · 2017-07-29 06:12:49Z

2

We'll write a little analog of Array#forEach, which iterates over the key/value pairs in an object in sorted order, and calls a function on each pair, passing it the key and its value:

function forEach(object, fn) {
  object.entries() . sort((a, b) => a[0] - b[0]) . forEach(pair => fn(...pair));
}

If you don't have Object#entries, the write it yourself:

function objectEntries(object) {
  return Object.keys(object) . map(key => [key, object[key]]);
}

Now to iterate over your object:

forEach(map, (year, yearValue) => 
  forEach(yearValue, (month, monthValue) => 
    console.log(`At ${year}/${month}, got data ${monthValue}`)));

edited Jul 29, 2017 at 6:12

answered Jul 28, 2017 at 18:42

user663031

Comments

anvita surapaneni · Accepted Answer · 2017-07-31 16:10:18Z

0

Javascript objects aren't ordered, so the first thing you will need to do is to grab the keys, sort them, and then iterate in that order.

 data = {
      2016: {
        3 : [
          { field: "content 1" },
          { field: "content 2" },
        ],
        10 : [
          { field: "content 3" },
        ],
      },
      2017: {
        8 : [
          { field: "content 4" },
        ],
      },
    };
    
    var keys = Object.keys(data);
    var sortedKeys = keys.sort(function(a, b) {return parseInt(a) - parseInt(b)});
    
    for (var i = 0; i < sortedKeys.length; i++) {
      var key = sortedKeys[i];
      console.log(data[key]);
    }

edited Jul 31, 2017 at 16:10

anvita surapaneni

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answered Jul 28, 2017 at 18:21

intentionally-left-nil

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