Assign to multiple values in object using destructure-like syntax

Question

Is there a cleaner way of setting the values a,b, and c in bar. Something similar to ES6 destructuring-assignment syntax?

bar = { foo: 10, a: 0, b: 0, c: 0, baz: 14 };

myFunc = (myObj) => {
    const { foo } = myObj;
    let a, b, c;
    a = 1 + foo;
    b = 2 + foo;
    c = 3 + foo;
    myObj.a = a;
    myObj.b = b;
    myObj.c = c;
}

myFunc(bar);

Assuming that bar has already been instantiated somewhere else, I'd like to set the new values without creating/assigning a new object to bar. We could do something like this myObj = {...myObj, a, b, c}, but that'd assign a new object to bar, from my understanding.

Given they are constants, how about const bar = {foo: 10, a: 11, b: 12, c: 13};? However, I think what you really are looking for are Self-references in object literal declarations — Bergi
– Bergi, Commented Oct 30, 2017 at 4:00
I think what you're looking for is How to assign multiple values to a JavaScript object? — Tigregalis
– Tigregalis, Commented Oct 30, 2017 at 4:54

Tigregalis · Accepted Answer · 2017-10-30 05:08:01Z

1

Based on this answer to a similar question, you can use Object.assign().

bar = { foo: 10, a: 0, b: 0, c: 0, baz: 14 };

myFunc = (myObj) => {
    const { foo } = myObj;
    let a, b, c;
    a = 1 + foo;
    b = 2 + foo;
    c = 3 + foo;
    Object.assign(myObj, {a: a, b: b, c: c});
}

myFunc(bar);

or of course

    const { foo } = myObj;
    Object.assign(myObj, {a: 1 + foo, b: 2 + foo, c: 3 + foo})

edited Oct 30, 2017 at 5:08

answered Oct 30, 2017 at 4:56

Tigregalis

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1 Comment

raychz Over a year ago

Object.assign(myObj, {a, b, c}); inside of myFunc did it for me! Wish it was prettier though.

yxre · Accepted Answer · 2017-10-30 03:51:55Z

0

ES6 did not bring in any features that would make this code simpler. There is one feature available, but it is a best practice not to use it. The with keyword

with (bar) {
 a = foo+1
 b = foo+2
 c = foo+3
}

The best way to make that code shorter would be to wrap the logic into a method call if it is being re-used a lot.

answered Oct 30, 2017 at 3:51

yxre

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2 Comments

Bergi Over a year ago

In every new ES6 syntax (like class or modules), with is strictly prohibited. For good reason.

raychz Over a year ago

Thanks, Leland. I'd like to avoid usage of with if possible.

Bergi · Accepted Answer · 2017-10-30 04:04:38Z

0

You can use an object literal shorthand and construct your object the other way round:

const foo = 10;
const a = 1+foo, b = 2+foo, c = 3+foo;
const bar = { foo, a, b, c };

which of course could be shortened to simply

const bar = { foo, a: 1+foo, b: 2+foo, c: 3+foo };

answered Oct 30, 2017 at 4:04

Bergi

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2 Comments

raychz Over a year ago

See my edit please. Let's assume bar has been created elsewhere. I'd like to streamline the assignments to a, b, and c in bar without creating a new object.

Bergi Over a year ago

Well you could do Object.assign(bar, {a,b,c}), but I think it's even simpler to just avoid those local variables and write bar.a = 1+foo; bar.b = 2+foo; bar.c = 3+foo;. I don't see what would be wrong with that (of course your example is a bit repetitive, I guess you'd need to show us your actual use case).

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