Generic function syntax in Typescript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a generic function in TypeScript?

A generic function is a function that can work with any data type, allowing you to write flexible and reusable code by using type variables.

beginner

How do you declare a generic function in TypeScript?

You declare a generic function by adding a type parameter inside angle brackets <T> before the function's parameters, like: <br>function example<T>(arg: T): T { return arg; }

beginner

What does the <T> mean in a generic function?

The <T> is a placeholder for a type that will be specified when the function is called. It stands for 'Type' and can be replaced with any type like number, string, or a custom type.

intermediate

Can a generic function have multiple type parameters? Give an example.

Yes, a generic function can have multiple type parameters separated by commas, like:<br>function pair(first: T, second: U): [T, U] { return [first, second]; }

intermediate

Why use generic functions instead of using 'any' type?

Generic functions keep type safety by preserving the type information, while 'any' disables type checking and can lead to errors. Generics help catch mistakes during coding.

What does the <T> represent in a TypeScript generic function?

A A placeholder for a type to be specified later

B A variable name

C A function name

D A keyword to declare a constant

The is a type parameter that acts as a placeholder for any type specified when the function is called.

How do you declare a generic function that returns the same type as its argument?

A function example(arg: number): number { return arg; }

B function example(arg: any): any { return arg; }

C function example<T>(arg: T): T { return arg; }

D function example<T>(arg: number): T { return arg; }

Option C correctly declares a generic function with type parameter T that returns the same type as the argument.

Can a generic function have more than one type parameter?

A Yes, separated by commas inside <>

B No, only one type parameter is allowed

C Yes, but only if they are the same type

D No, you must use multiple functions instead

Generic functions can have multiple type parameters separated by commas, like .

What is the main advantage of using generic functions over 'any' type?

A They use less memory

B They run faster

C They allow any value without restrictions

D They keep type safety and help catch errors

Generics preserve type information, helping the compiler catch errors, unlike 'any' which disables type checking.

Which of the following is a valid generic function syntax in TypeScript?

A function identity(arg: T): T { return arg; }

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

C function identity<T>(arg): T { return arg; }

D function identity(arg): arg { return arg; }

Option B correctly declares a generic function with type parameter T and typed argument and return.

Explain how to write a generic function in TypeScript and why it is useful.

Think about how you can make a function work with different types without repeating code.

Describe the difference between using a generic type parameter and the 'any' type in a function.

Consider how TypeScript helps you avoid mistakes.