no-explicit-any in generic function which returns list size

Question

I have a simple function which returns array's length

const test = (list: any[]) => list.length;

Which generates eslint error:

no-explicit-any: Unexpected any. Specify a different type. (javascript-eslint)

What would be the correct way to write this function in TypeScript?

Answer 1

Use generics:

const test = <T>(list: T[]): number => list.length;

Then you can call function like:

test([1, 2, 3]) // or test<number>([1, 2, 3]);
test(["s1", "s2", "s3"]); // or test<string>(["s1", "s2", "s3"]);
test([{ 
  key1: 'k1', 
  key2: 'k2',
}]);