CODEWITHSUNDEEP
javascriptecmascript-6destructuring
alanbuchanan
alanbuchanan

Reputation: 4173

Destructuring an object without specifying its properties

Is there an elegant solution to destructure an object without specifying all the object's properties?

I wondered if it was possible to use the spread operator but it seems like that's not possible because objects are not arrays!

I guess it may be considered a bad idea to blindly declare variables but I think this would be useful for very large objects.

Upvotes: 3

Views: 369

Answers (1)

Ven
Ven

Reputation: 19039

This is what the with(){} construction allowed:

var obj = {a: 1};
with (obj) {
  console.log(a);
}

This construct is however severely discouraged and basically deprecated (it throws an error in strict mode), because it has some major drawbacks:

  • Your code is hard to read, because it's impossible to tell apart 1) Variables from outer scopes 2) Local variables 3) Properties coming from the object.

  • Your code can't be optimized, because the JavaScript engine can't tell where your variables are coming from.

  • Your code is much harder to refactor, because if you introduce a property to your obj, it might shadow some existing local variable, exemple:

var obj = {};
var a = 1;
addSomeProperties(obj);
with (obj) {
  console.log(a); // the result here depends on whether or not "addSomeProperties" puts a property named "a" on "obj"
}

TL;DR version: you really don't want this, it makes your code brittle, hard to read&refactor. Just pick the pieces you want apart using the "normal" destructuring syntax.

Upvotes: 7

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