CODEWITHSUNDEEP
arraysvue.jsecmascript-6
drake035
drake035

Reputation: 2877

Splitting an array of objects based on unique combinations of two properties

For my time-tracking app, I'm storing time entries in an array of objects each looking like this:

{
  date: "20181206",
  hours: "4",
  projectId: "65WchP9X46HlOYUzmWrL",
  taskId: "fJTU7wggJHbg1uRuRUdHjS5mn8J3"
}

I need to group, into separate arrays, all objects by unique combinations of ProjectId - TaskId properties, so that each resulting array gets all entries for one particular project and one particular task (an array for project #1 / task #1, another for project #1 / task #2, another for project #2 / task #1, etc).

I know how to do that with one property, but is there a simple way to achieve the same with two properties?

Note: my global array is initially populated like so:

weekTimes = [];
querySnapshot.forEach((doc) => {
  weekTimes.push(doc.data());
});

Upvotes: 0

Views: 171

Answers (1)

akuiper
akuiper

Reputation: 214927

Create a composite key from projectId and taskId: 

grouped = {}

for (weekTime of weekTimes) {
  var key = `${weekTime.projectId}/${weekTime.taskId}`

  if (grouped[key] === undefined) {
    // if the key doesn't exist, weekTime is the first item, create the key 
    // and assign an array with the first item to it
    grouped[key] = [ weekTime ]
  } else {
    // if the key already exists in grouped, just push new item to that key
    grouped[key].push(weekTime)
  }
}

// if you don't need the keys
Object.values(grouped)

Or use lodash groupby:

const _ = require('lodash')

_.groupBy(weekTimes, x => x.projectId + '/' + x.taskId)

Upvotes: 1

Related Questions