Parameters type in Typescript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does 'Parameters type' mean in TypeScript?

It means specifying the type of values that a function expects as inputs, so the function knows what kind of data it will receive.

beginner

How do you write a function in TypeScript that takes a number as a parameter?

You write the parameter name followed by a colon and the type. Example: <pre>function double(x: number) { return x * 2; }</pre>

beginner

What happens if you pass a wrong type to a function with typed parameters in TypeScript?

TypeScript will show an error before running the code, helping you fix the mistake early.

intermediate

Can function parameters in TypeScript have optional types?

Yes, you can mark parameters as optional with a question mark. Example: <pre>function greet(name?: string) { ... }</pre>

beginner

What is the benefit of using parameter types in functions?

It helps catch mistakes early, makes code easier to understand, and improves code quality by ensuring correct data is used.

How do you specify a string parameter named 'text' in a TypeScript function?

A function example(text) {}

B function example(string text) {}

C function example(text = string) {}

D function example(text: string) {}

In TypeScript, you write the parameter name followed by a colon and the type.

What does the question mark (?) mean in a parameter like 'name?: string'?

A The parameter is optional

B The parameter is required

C The parameter is a number

D The parameter is a default value

The question mark marks the parameter as optional, so it can be omitted.

What will TypeScript do if you pass a number to a function expecting a string parameter?

A Crash the program at runtime

B Convert the number to string automatically

C Show a type error before running

D Ignore the type and run anyway

TypeScript checks types before running and shows errors if types don't match.

Which of these is a correct way to define a function with two parameters: a number and a boolean?

A function check(num, flag) {}

B function check(num: number, flag: boolean) {}

C function check(number num, boolean flag) {}

D function check(num: boolean, flag: number) {}

You specify each parameter name followed by its type separated by commas.

Why is it helpful to use parameter types in functions?

A To catch errors early and understand code better

B To make code run faster

C To allow any type of input without errors

D To make functions shorter

Parameter types help catch mistakes early and improve code clarity.

Explain how to define a function with typed parameters in TypeScript and why it is useful.

Think about how you tell the function what kind of data it should expect.

Describe what happens if you pass the wrong type of argument to a function with typed parameters in TypeScript.

Consider how TypeScript helps you avoid bugs.