@studnicky/v8/array-spread-outside-loops

Disallows a spread element in an array literal that is assigned to an identifier or property, or initializes a variable, when that expression executes once per iteration. Repeatedly rebuilding an array with [...result, item] allocates and copies the growing prefix on every iteration, producing quadratic work. A built-in per-element iteration callback is treated as a loop body.

The rule targets only bound array literals. Spread passed as a call argument, such as result.push(...items), and nested or unbound literals are outside its scope.

Fixable: No · Options: No · Suggested severity: error

✗ Incorrect

let result: string[] = [];
for (const item of items) {
  result = [...result, item];
}

let result: string[] = [];
items.forEach((item) => {
  result = [...result, item];
});

✓ Correct

const result: string[] = [];
for (const item of items) {
  result.push(item);
}

const merged = [...first, ...second];