proposal-array-grouping
A proposal to make grouping of items in an array easier.
const array = [1, 2, 3, 4, 5];
// groupBy groups items by arbitrary key.
// In this case, we're grouping by even/odd keys
array.groupBy((num, index, array) => {
return num % 2 === 0 ? 'even': 'odd';
});
// => { odd: [1, 3, 5], even: [2, 4] }
// groupByToMap returns items in a Map, and is useful for grouping using
// an object key.
const odd = { odd: true };
const even = { even: true };
array.groupByToMap((num, index, array) => {
return num % 2 === 0 ? even: odd;
});
// => Map { {odd: true}: [1, 3, 5], {even: true}: [2, 4] }Champions
- Justin Ridgewell (@jridgewell)
Status
Current Stage: 3
Motivation
Array grouping is an extremely common operation, best exemplified by
SQL's GROUP BY clause and MapReduce programming (which is better
thought of map-group-reduce). The ability to combine like data into
groups allows developers to compute higher order datasets, like the
average age of a cohort or daily LCP values for a webpage.
Two methods are offered, groupBy and groupByToMap. The first returns a
null-prototype object, which allows ergonomic destructuring and prevents
accidental collisions with global Object properties. The second returns
a regular Map instance, which allows grouping on complex key types
(imagine a compound key or tuple).
Polyfill
- A polyfill is available in the core-js library. You can find it in the ECMAScript proposals section.
Related
- Lodash