unicorn/prefer-native-coercion-functions

A function that only passes its first parameter to String, Number, BigInt, Boolean or Symbol does what the built-in already does. Pass the built-in itself.

The rule also reports value => value as the callback of every, filter, find, findIndex, findLast, findLastIndex and some. Those methods only check whether the result is truthy, so Boolean does the same thing.

Configure

Off by default. To turn it on:

[lint.rules]
"unicorn/prefer-native-coercion-functions" = "error" # or "warn"

Examples

Reported:

const ids = rows.map(id => Number(id));

const names = users.map(user => user.name).filter(name => name);

function toText(value) {
  return String(value);
}

Not reported:

const ids = rows.map(Number);

const names = users.map(user => user.name).filter(Boolean);

const toText = String;

A function that does anything more isn't reported. Neither is a TypeScript type guard, because Boolean doesn't narrow the type:

const prices = rows.map(row => Number(row.price));

const found = items.filter((item): item is Item => Boolean(item));