prefer-array-flat-map.md

Prefer .flatMap(…) over .map(…).flat()

✅ This rule is part of the recommended config.

🔧 This rule is auto-fixable.

Array#flatMap performs Array#map and Array#flat in one step.

Fail

const foo = bar.map(element => unicorn(element)).flat();

const foo = bar.map(element => unicorn(element)).flat(1);

Pass

const foo = bar.flatMap(element => unicorn(element));

const foo = bar.map(element => unicorn(element)).flat(2);

const foo = bar.map(element => unicorn(element)).foo().flat();

const foo = bar.flat().map(element => unicorn(element));

Related rules

• unicorn/prefer-array-flat