Generic arrow functions in Typescript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a generic arrow function in TypeScript?

A generic arrow function is a function written with arrow syntax that uses type parameters to work with different data types while keeping type safety.

beginner

How do you declare a generic arrow function with one type parameter <T>?

You write the function with <T> before the parameters, like: <br><code>const func = &lt;T&gt;(arg: T): T =&gt; arg;</code>

intermediate

Why use generic arrow functions instead of regular functions?

Generic arrow functions provide concise syntax and allow type flexibility with less code, making them easy to read and maintain.

beginner

What does this generic arrow function do?<br><code>const identity = &lt;T&gt;(value: T): T =&gt; value;</code>

It returns the same value it receives, keeping the type of the input and output the same.

intermediate

Can generic arrow functions have multiple type parameters? Give an example.

Yes, for example:<br><code>const pair = &lt;T, U&gt;(first: T, second: U): [T, U] =&gt; [first, second];</code>

How do you start declaring a generic arrow function with type parameter T?

A const func = <T>(arg: T) => arg;

B function func<T>(arg: T) { return arg; }

C const func = (arg: T) => arg;

D const func = (T) => arg;

Generic arrow functions use before the parameters to declare the type parameter.

What does the generic arrow function <T>(arg: T): T => arg; do?

A Throws an error.

B Converts the argument to string.

C Returns the argument with the same type.

D Returns a number always.

It returns the input argument without changing its type.

Can generic arrow functions have more than one type parameter?

A Yes, like <T, U>.

B No, only one type parameter is allowed.

C Only if you use function keyword.

D Only in classes.

Generic arrow functions can have multiple type parameters separated by commas.

Which of these is a valid generic arrow function syntax?

A const func = (arg: T) <T> => arg;

B const func = (T)<arg>: T => arg;

C const func = <T> arg: T => arg;

D const func = <T>(arg: T): T => arg;

Option D correctly places before the parameters and uses arrow syntax.

What is the main benefit of using generic arrow functions?

A They run faster than normal functions.

B They allow writing flexible, type-safe functions with concise syntax.

C They do not require type annotations.

D They only work with strings.

Generic arrow functions combine flexibility and type safety with short syntax.

Explain how to write a generic arrow function that returns the input value unchanged.

Think about how to declare <T> and use it in parameters and return type.

Describe the advantages of using generic arrow functions in TypeScript.

Consider why generics and arrow functions are useful together.