JavaScript: Map an array of objects to a dictionary

#javascript #typescript #data

The easiest way for converting an array of objects to a dictionary in JavaScript / TypeScript:

let data = [
  {id: 1, country: 'Germany', population: 83623528},
  {id: 2, country: 'Austria', population: 8975552},
  {id: 3, country: 'Switzerland', population: 8616571}
];

let dictionary = Object.assign({}, ...data.map((x) => ({[x.id]: x.country})));
// {1: "Germany", 2: "Austria", 3: "Switzerland"}

Top comments (6)

Ritchie Paul Buitre • Nov 15 '22

Nice, instead how about using Object.fromEntries like so:

let dictionary = Object.fromEntries(data.map(x => [x.id, x.country]));

Olga Farber • Oct 26 '22

how beautiful! thank you for the idea! and implementation :)

Aria Janke • Apr 4 '22

terse, and to the point
thank you

Luiz • Mar 13 '22

thanks

Odey • Jul 31 '22

Hey!! can you explain please why did you use the Rest parameter syntax with ...data?

Olga Farber • Oct 26 '22

it's because data is an array, so its map is also an array, and when you use ...data - it spreads the array elements to be function parameters, which get to be one-prop objects, with which the resulting object is updated. Beautiful!

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JavaScript: Map an array of objects to a dictionary

Top comments (6)

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