Constructing object based on true/false conditions

Question

I am usually constructing objects that do have fields in them or do not have them based on a condition so

let data
if(something === true) {
  data = {
    name: 'String',
    something: 'Something'
  }
else {
  data = {
    name: 'String'
  }
}

but this seems like a very "dirty way to do this" as data needs to be redefined every time + if there were more if conditions this would become quiet big chunk of code. Is there a more concise way to achieve this?

Why not assign the common values first, then just add the additional ones later. `var data = {name: 'String'}; if(something){ data.something = 'Something'; }`? — gen_Eric, Jun 01 '16 at 15:27
Simplest way is to let data = {}; and then in your if, just do data.name='String'; data.something = 'Something' etc etc But there are tons of ways to skin this cat. — Tad Donaghe, Jun 01 '16 at 15:27
There is no such thing as a [JSON object](http://stackoverflow.com/q/2904131/1048572). And what you have here isn't JSON anyway (lacking quotes). — Bergi, Jun 01 '16 at 15:31

score 3 · Accepted Answer · answered Jun 01 '16 at 15:27

3

Just conditionally add properties to the object - you don't need to define the whole thing in one go as an object literal.

let data = {
    name: 'String'
};
if (something) {
    data.something = 'Something';
}

answered Jun 01 '16 at 15:27

Bergi

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Of course, but there's something vaguely unsatisfying about this. – Jun 01 '16 at 16:04
@torazaburo: The repetition of the identifier `data` maybe? I like your approach, but for some reason I probably still wouldn't use it. – Bergi Jun 01 '16 at 16:11

maioman · Answer 2 · 2016-06-01T15:52:30.537

0

you can use can a ternary operator like this:

let data = {
  name: 'String',
  something: (something) ? "Something" : undefined,
}

practically this should work because undefined is what you get when trying to access a non-existing object property,
but keep in mind you're adding an enumerable property to the object.

edited Jun 01 '16 at 15:52

answered Jun 01 '16 at 15:34

maioman

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You should not use that unless you know how it is different from the original result, though. – Bergi Jun 01 '16 at 15:38
@Bergi the difference is that property exists but is undefined, or is there something else? – maioman Jun 01 '16 at 15:45
Yes, that's what I meant. You should add a paragraph about that in your answer. – Bergi Jun 01 '16 at 15:47

score 0 · Answer 3 · 2016-06-01T16:24:15.957

0

You can use Object.assign as follows, because it ignores non-object parameters:

let data
let something = true
data = Object.assign(
    { name: 'String' },
    something && {something: 'Something'}
)

console.log(data)

Or, if you prefer

something ? {something: 'Something'} : {}

edited Jun 01 '16 at 16:24

answered Jun 01 '16 at 16:01

Constructing object based on true/false conditions

3 Answers3