JS return object by array index

Question

I'm trying to convert an array to an object (keyed by the first element).

foo = [1,2]

function convert_foo(foo) {
    return { foo[0]: foo[1] };
}

The following is not valid Javascript: Uncaught SyntaxError: Unexpected token [.

I've also tried:

function convert_foo(foo) {
    return ({ foo[0]: foo[1] });
}

EDIT:

It's possible this way, but I was wondering if there was a way to return it in one line.

function convert_foo(foo) {
    var obj = {}
    obj[foo[0]] = foo[1];
    return obj;
}

Robby Cornelissen · Accepted Answer · 2019-06-14 03:00:41Z

4

For dynamic keys (aka computed property names in ECMAScript 2015), you have to put the key in square brackets:

function convert_foo(foo) {
    return { [foo[0]]: foo[1] };
}

console.log(convert_foo([1, 2]));

answered Jun 14, 2019 at 3:00

Robby Cornelissen

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3 Comments

Thanks I'll accept it. Is there a way to use this with map? i.e. foo_array.map(foo => { [foo[0]]: foo[1] })?

With map(), you mean mapping an array to an object with multiple properties?

I just found it. foo_array.map(foo => ({ [foo[0]]: foo[1] })). Wrapping the return ().

Shidersz · Accepted Answer · 2019-06-14 03:11:50Z

1

With the upcoming Object.fromEntries(), that is already supported on some browsers, you can also do something like this:

function convert_foo(foo)
{
    return Object.fromEntries([foo]);
}

console.log(convert_foo([1, 2]));

.as-console {background-color:black !important; color:lime;}
.as-console-wrapper {max-height:100% !important; top:0;}

answered Jun 14, 2019 at 3:11

Shidersz

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