turning an array into an object using es6 map

Question

I currently have the following data structure:

const bar = [
    {id:1, version:0, name:"test name A"},
    {id:2, version:0, name:"test name B"},
    {id:3, version:0, name:"test name C"}
];

And I need to turn it into this:

const foo = {
    1:{id:1, version:0, name:"test name A"},
    2:{id:2, version:0, name:"test name B"},
    3:{id:3, version:0, name:"test name C"}
};

The piece of code I actually have is this:

for(let i=0;len = bar.length; i< len;i++){
    foo[bar[i].id]= bar[i];
}

I've tried doing

bar.map((element,index)=>{
    const temporal = {[index]:element};
    foo = {...foo, temporal};
});

but I'm lost, any suggestions?

Are you talking about using Array.map or the new ES6 Map structure? There seems to be some confusion. Because you can just do bar.reduce((m, o) => m.set(o.id, o), new Map()); if you want the latter. Array.map has been around long before ES6. — Andy
– Andy, Commented Sep 26, 2017 at 16:34
@adeneo I don't want to. It's a data structure I need to pass to an API. — Anyul Rivas
– Anyul Rivas, Commented Sep 26, 2017 at 17:05
@OriDrori, ha! I was just impressed with your code from earlier as you might have guessed. Kudos for keeping me on my toes. That was a great answer earlier btw. — Andy
– Andy, Commented Sep 26, 2017 at 17:10

Nenad Vracar · Accepted Answer · 2017-09-26 16:30:31Z

4

You can use reduce() with Object.assign()

const bar = [
    {id:1, version:0, name:"test name A"},
    {id:2, version:0, name:"test name B"},
    {id:3, version:0, name:"test name C"}
];

var result = bar.reduce((r, e) => Object.assign(r, {[e.id]: e}), {});
console.log(result)

answered Sep 26, 2017 at 16:30

Nenad Vracar

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Comments

Nina Scholz · Accepted Answer · 2017-09-26 16:31:24Z

2

You could use Object.assign with Array#map and spread syntax ...

const
    bar = [{ id: 1, version: 0, name: "test name A" }, { id: 2, version: 0, name: "test name B" }, { id: 3, version: 0, name: "test name C" }],
    object = Object.assign(...bar.map(o => ({ [o.id]: o })));

console.log(object);

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

answered Sep 26, 2017 at 16:31

Nina Scholz

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Comments

ichigolas · Accepted Answer · 2017-09-26 16:30:58Z

1

You can use reduce, aka fold or inject in general:

const bar = [
    {id:1, version:0, name:"test name A"},
    {id:2, version:0, name:"test name B"},
    {id:3, version:0, name:"test name C"}
];

bar.reduce((obj, e, i) => { obj[e.id] = e; return obj}, {});

answered Sep 26, 2017 at 16:30

ichigolas

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Comments

andrewatkinson · Accepted Answer · 2017-09-26 16:40:20Z

1

Another way could be to use forEach which iterates over the array, but doesn't return an array as map does:

let foo = {};
bar.forEach((el, idx) => foo[idx+1] = el)

answered Sep 26, 2017 at 16:40

andrewatkinson

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Comments

adeneo · Accepted Answer · 2017-09-26 17:25:09Z

1

Array.map returns an array, if you wanted to return an object, you could use Array.reduce instead

const bar = [
    {id:1, version:0, name:"test name A"},
    {id:2, version:0, name:"test name B"},
    {id:3, version:0, name:"test name C"}
];

var foo = bar.reduce( (a,b,i) => (a[i+1] = b, a), {});

console.log(foo);

If you just need to reformat the data for sending it to an API, there's no need to create true clones of the objects with Object.assign

edited Sep 26, 2017 at 17:25

answered Sep 26, 2017 at 16:29

adeneo

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