Is this a new way to extend an object in JavaScript?

Question

While upgrading a private yeoman generator I stumpled upon this statement while looking through the official generator-webapp:

const { features } = answers;

I wasn't able to find anything about this, aside from the fact that it only works on node >=6.

What does this statement do? Where is this defined?

T.J. Crowder · Accepted Answer · 2017-06-06T13:48:53.640

3

It's destructuring assignment. It's equivalent to:

const features = answers.features;

It was introduced in ES2015.

edited Jun 06 '17 at 13:48

answered Jun 06 '17 at 13:41

T.J. Crowder

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Thank you very much. Will accept as soon as the timeout has passed… ;-) – nietonfir Jun 06 '17 at 13:41
@nietonfir: No worries. BTW, no idea what I was thinking, object destructuring was in ES2015 along with array destructuring. (Brain a bit fuzzy today.) *(Edit: Ah, I know what I was thinking of: [Spread and rest properties](https://github.com/tc39/proposal-object-rest-spread), which unlike spread and rest for arrays, are still just a proposal.)* – T.J. Crowder Jun 06 '17 at 13:43

score 1 · Answer 2 · answered Jun 06 '17 at 13:46

This:

const { features } = answers;

Is the shorthand of this:

const features = answers.features;

You could also declare many variables in a single line, see following please:

var answers = {"features": "test"};
const { features } = answers;
console.log(features);

var longObj = {"attr1": "val1", "attr2" : "val2"};
const { attr1, attr2 } = longObj;
console.log(attr1, attr2);

I hope it was clear. Bye.

Is this a new way to extend an object in JavaScript?

2 Answers2