TypeScript · Junior · Question 64 of 75

Why can `[1, 2].forEach((n) => console.log(n))` pass a callback with one parameter when `forEach` passes three?

✓Correct answer: A function with fewer parameters is assignable to a function type with more - extra arguments are simply ignored
2TypeScript adds the missing parameters
3forEach only passes one argument

Explanation

This mirrors common JavaScript practice. The opposite (a callback requiring more parameters than provided) is an error.

Further reading

TS: Type Compatibility ↗

Test yourself

Take the TypeScript · Junior quiz: questions and options are shuffled, and you get a review of your mistakes at the end.