javascript - Chain of [key1, value1, key2, value2, ...] to object - Stack Overflow

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I am a bit stuck in finding a simple and elegant way to convert an Array like

const array = ["k1", "v1", "k2", "v2"]

to an object

const obj = {"k1": "v1", "k2": "v2"}

Just looking for inspirations

I am a bit stuck in finding a simple and elegant way to convert an Array like

const array = ["k1", "v1", "k2", "v2"]

to an object

const obj = {"k1": "v1", "k2": "v2"}

Just looking for inspirations

• javascript

Share Improve this question Follow edited Aug 20, 2020 at 22:12 webdeb asked Aug 20, 2020 at 22:03 webdebwebdeb 13.2k55 gold badges2929 silver badges4444 bronze badges

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6 Answers 6

Sorted by: Reset to default 6

Maybe the good-old for-loop ?

To recap the proposed solutions

for-loop (clean & readable)

const obj = {}
for (let i = 0; i < array.length; i += 2) {
  obj[array[i]] = array[i + 1]
}

Array.reduce (oneliner, but a bit cryptic)

const obj = array.reduce((acc, curval, idx, arr) => (idx % 2) == 0 ? 
                             (acc[curval] = arr[idx+1], acc) : acc, {});

_.chunk + Object.fromEntries

I like this solution the most, but it has lodash as dependency. Would be cool if ES could implement it natively array.chunk(2)

Object.fromEntries(_.chunk(array))

A bit long to really be called a one-liner but if you can find a nice way to chunk the array into pairs then you can just give that to Object.fromEntries. Something like lodash's _.chunk would make this look a lot better but barring that:

const array = ["k1", "v1", "k2", "v2"]

const obj = Object.fromEntries(Array.from({length: array.length / 2}, (_, i) => array.slice(i, i+2)))
console.log(obj);

With Array.reduce():

const array = ["k1", "v1", "k2", "v2"];
var newarr = array.reduce((acc, curval, idx, arr) => (idx % 2) == 0 ? 
                             (acc[curval] = arr[idx+1], acc) : acc, {});

console.log(newarr);

You can acplish this with the code below:

const array = ["k1", "v1", "k2", "v2"];
let obj = {};

for (let i = 0; i < array.length; i+=2) {
  obj[array[i]] = array[i+1];
}

console.log("Array: "+array);
console.log("\nObject: "+array);
console.log("    k1: "+obj["k1"]);
console.log("    k2: "+obj.k2);

Not so elegant, but might lead for farther thoughts:

Using map, reduce, and lodash merging:

let array = ["a1", "b1", "a2", "b2"];

array = array.map((e,i)=>{
    let newobj={};
    newobj[e]=array[i+1];
    return i%2===0?newobj:{}
});

array.reduce((v1,v2)=>_.merge(v1, v2));

(Assuming an even number of elements in array)

Using a function like chunk, but with pure Js:

const array = ["k1", "v1", "k2", "v2"]
function chunks(arr, size = 2) {
  return arr.map((x, i) => i % size == 0 && arr.slice(i, i + size)).filter(x => x)
}
console.log(Object.fromEntries(chunks(array)))

And this one is using flatMap():

const array2 = ["k1", "v1", "k2", "v2"]

const pairs = (arr)=>{return arr.flatMap((_, i, a) => i % 2 ? [] : [a.slice(i, i + 2)])}
console.log(Object.fromEntries(pairs(array2)))

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