Grouping Array Data — JSON

Umar TaufiqFollow

Jul 16, 2018

CASE: We want to reorganise a JSON Array i.e. Sort Array items into groups

Suppose the following:

1. You have created an array.
2. This array has all the information you require.
3. However you forgot to group the information.

In other words, you have something like this:

But you want something like this:

How can this be done?

This can be done via the combination of 4 functions:

1. groupBy

2. mapValues

3. map

4. omit

groupBy, mapValues and omit are available in the js library lodash.

1. Grouping the players array:

_.groupBy(players, "team");

This applies lodash’s groupBy function to the players array using the property team

Quotation marks are important

Here’s a different way to look at this function:

const Array = players;
const Property = "team";
const playersByTeam = _.groupBy(Array, Property);

No matter which way you choose to do it, the result will be:

This may look good but our problem here is that the need for the teamproperty has been eliminated, so the team property in the newly created object is a waste of space.

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In a large application, keeping the team property would be wasting a lot of space and filling the application with data that has become irrelevant.

2. Mapping Values

The following is an example of how we might use _.mapValues

_.mapValues(playersByTeam, x => "foo");

This will get each object in playersByTeam and change it to “foo”

 

In our case we don’t want to change it to “foo”, we want to change it to an object that does not contain the team property.

3. Map

_.mapValues(playersByTeam, x => x.map(y => "bar"));

If we run this in the console we can see:

 

This means we can create an object {} based on playersByTeam and change the array [] in the object.

4. Omit

The _.omit function creates an object without a certain property, in our case, the property is team.

_.mapValues(playersByTeam, x => x.map(y => _.omit(y, 'team') ));

 

That’s the console version of:

In conclusion,

to create a reorganised array without the team property you need

_.mapValues(_.groupBy(players, "team"), x => x.map(y => _.omit(y, "team") ));

[출처] https://codeburst.io/grouping-array-data-json-ef96b438b927