Create object from array
Simply
const obj = {}; for (const key of yourArray) { obj[key] = whatever; }
or if you prefer "functional" style:
const obj = yourArray.reduce((o, key) => Object.assign(o, {[key]: whatever}), {});
using the modern object spread operator:
const obj = yourArray.reduce((o, key) => ({ ...o, [key]: whatever}), {})
Example:
[ { id: 10, color: "red" }, { id: 20, color: "blue" }, { id: 30, color: "green" }].reduce((acc, cur) => ({ ...acc, [cur.color]: cur.id }), {})
Output:
{red: 10, blue: 20, green: 30}
Here is how it works:
reduce
is initialized with an empty object (empty {}
at the end), therefore first iteration variables are acc = {}
cur = { id: 10, color: "red" }
. Function returns an object - this is why function body is wrapped in parentheses => ({ ... })
. Spread operator doesn't do anything on the first iteration, so red: 10
is set as first item.
On the second iteration variables are acc = { red: 10 }
cur = { id: 20, color: "blue" }
. Here the spread operator expands acc
and the function returns { red: 10, blue: 20 }
.
Third iteration acc = { red: 10, blue: 20 }
cur = { id: 30, color: "green" }
, so when acc
is spread inside the object, our function returns the final value.
The new Object.fromEntries
, from ECMAScript 2019, makes it even easier to transform values from an array into keys in an object like follows
const dynamicArray = ["2007", "2008", "2009", "2010"];const obj = Object.fromEntries( dynamicArray.map(year => [year, { something: "based", on: year }]))console.log(obj)
in js with es6 reduce function for array I do it like this
let x = [1,2,3]let y = x.reduce((acc, elem) => { acc[elem] = elem // or what ever object you want inside return acc}, {})console.log(y) // {1:1, 2:2, 3:3}