Array methods over single-statement loops

A loop whose body is one statement, with no break, continue, return or await, can usually be written as an array method.

Why it is a rule

The array method names the operation. map says a value comes back per element, filter says some are dropped, forEach says nothing is returned. A bare for says only that something repeats, and leaves the reader to work out which case applies.

What is expected

forEach, map, filter, flatMap or reduce, whichever names what the loop does.

Why it ships as a warning

The check is syntactic and cannot know what the loop iterates. A Set, a Map or a generator has no map or filter, so a single-statement loop over one can be flagged even though a direct rewrite is not possible. Convert with [...iterable] where that reads well, use the ignore marker where it does not, and raise the rule to error in config once your codebase's loops are mostly over arrays. If you run Biome's noForEach or a similar rule pointing the opposite way, keep only one of the two.

Exceptions

This is not a ban on loops. Bodies with control flow are left alone, because they cannot be expressed as an array method. A hot path where a per-iteration closure allocation is a measured cost is a legitimate exception:

// vibator-ignore: hot path, runs per audio frame of a live call
for (let index = 0; index < input.length; index++) {

The reason is required.