arrayFlatUnnecessaryDepths

Reports using 1 as the depth argument of .flat() since it is the default.

✅ This rule is included in the ts stylistic presets.

The default depth for Array.prototype.flat() is 1, so passing it explicitly is redundant. This rule reports when 1 is passed as the depth argument to .flat().

Examples

❌ Incorrect

declare const array: number[][];
array.flat(1);

declare const array: number[][] | undefined;
array?.flat(1);

✅ Correct

declare const array: number[][];
array.flat();

declare const array: number[][][];
array.flat(2);

declare const array: number[];
array.flat(Infinity);

Options

This rule is not configurable.

When Not To Use It

If you prefer to be explicit about the depth argument for readability or consistency, you may disable this rule.

Further Reading

• MDN: Array.prototype.flat()

Equivalents in Other Linters

• ESLint: unicorn/no-unnecessary-array-flat-depth
• Oxlint: unicorn/no-unnecessary-array-flat-depth