Filling in missing objects in an array using Underscore

Question

I'm playing with a data set that counts the number of commits a person makes at a certain hour. I can create an array objects for the hour a person made a commit and how many times they committed:

[ { hour: '6', commits: 2 },
  { hour: '7', commits: 6 },
  { hour: '8', commits: 6 },
  { hour: '9', commits: 4 },
  { hour: '10', commits: 4 },
  { hour: '11', commits: 6 },
  { hour: '12', commits: 18 },
  { hour: '13', commits: 18 },
  { hour: '14', commits: 14 },
  { hour: '15', commits: 30 },
  { hour: '16', commits: 24 },
  { hour: '17', commits: 18 },
  { hour: '18', commits: 24 },
  { hour: '19', commits: 22 },
  { hour: '20', commits: 6 },
  { hour: '21', commits: 16 },
  { hour: '22', commits: 8 } ]

Where I'm stuck is trying to fill in the missing hours. So in the example above, I would need to include the hours where no commits were made. I'm using a 0-24 range for an entire day. This is what I'm hoping to get as a result:

[
  { hour: '0', commits: 0 }, 
  { hour: '1', commits: 0 },
  { hour: '2', commits: 0 },
  { hour: '3', commits: 0 },
  { hour: '4', commits: 0 },
  { hour: '5', commits: 0 },
  { hour: '6', commits: 2 },
  { hour: '7', commits: 6 },
  { hour: '8', commits: 6 },
  { hour: '9', commits: 4 },
  { hour: '10', commits: 4 },
  { hour: '11', commits: 6 },
  { hour: '12', commits: 18 },
  { hour: '13', commits: 18 },
  { hour: '14', commits: 14 },
  { hour: '15', commits: 30 },
  { hour: '16', commits: 24 },
  { hour: '17', commits: 18 },
  { hour: '18', commits: 24 },
  { hour: '19', commits: 22 },
  { hour: '20', commits: 6 },
  { hour: '21', commits: 16 },
  { hour: '22', commits: 8 },
  { hour: '23', commits: 0 },
  { hour: '24', commits: 0 }
]

Here is the function I'm using to create these objects:

var getAuthorAndHourCounts = (groupedByAuthor) => {

  var result = _.map(groupByAuthor, (value, key, list) => {

    var author = key;
    var hours = _.countBy(value, 'hour');

    var commitHourList = [];

    _.each(hours, (v,k) => {
      var obj = {};
      obj.hour = k;
      obj.commits = v;
      commitHourList.push(obj);
    });

    return {
      person: author,
      times: commitHourList
    };

  });
  return result;
};

How can I add the missing times? I was thinking of creating a list (0-24) and then seeing if an hour is not in the list to add it with a value of zero to the object. Not sure how that can be accomplished.

just a side note: you realize that there are 25 hours in your list, not 24... what's the difference between `hour:0` and `hour:24`? — Wh1T3h4Ck5, Sep 03 '16 at 02:02
Thank you for catching that. I intend to use 24 hours. 0 will be midnight, 1 will be 1 a.m., etc. — , Sep 06 '16 at 07:27

score 2 · Accepted Answer · edited May 23 '17 at 11:53

How about just initializing commitHourList such that it contains all hours with 0 commits and then fill it up with actual data:

// initialize commitHourList with 24 objects 
// one for each hour and each with 0 commits
var commitHourList = _.range(24).map((hour) => ({ hour, commits: 0 }));

// for every received hour, add proper commits
_.each(hours, (commits, hour) => {
  commitHourList[hour].commits = commits;
});

This way, whatever hour you don't add will automatically have 0 commits.

Note: using range then map to initialize the array is less code but does iterate the array twice each time. A more performant way would be to create this array once in some utility and then copy it each time you need a new one.

For example:

// utility that creates the hours array when initialized
// and returns a function that will return a copy of the hours array on each call
var getHoursArray = (function() {
  var arr =  _.range(24).map((hour) => ({ hour, commits: 0 }));
  return function() {
    return arr.slice();
  }
})();

And then use it like:

var commitHourList = getHoursArray();

Using slice is usually the most performant way of copying an array but here are other possibilities

seems logical, it will certainly avoid checking and re-filling missing data — Wh1T3h4Ck5, Sep 03 '16 at 02:04

Filling in missing objects in an array using Underscore

1 Answers1