Pick type in Typescript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the Pick type do in TypeScript?

The Pick type creates a new type by selecting specific properties from an existing type. It helps to focus on only the needed parts of a type.

beginner

How do you use Pick to select properties 'name' and 'age' from a type Person?

You write: <br>type PersonInfo = Pick<Person, 'name' | 'age'>;<br>This creates a new type with only name and age from Person.

intermediate

Why is Pick useful in real projects?

It helps to reuse existing types but only keep the parts you need. This makes code simpler and safer by avoiding extra properties.

intermediate

What happens if you try to Pick a property that does not exist in the original type?

TypeScript will give an error because you can only pick keys that exist in the original type.

advanced

Can Pick be combined with other utility types?

Yes! You can combine Pick with types like Partial or Readonly to create flexible and precise types.

What does Pick<T, K> do in TypeScript?

A Creates a new type with only the properties K from type T

B Removes properties K from type T

C Makes all properties in T optional

D Combines two types T and K

Pick selects specific properties K from type T to create a new type.

Which syntax correctly picks properties 'id' and 'title' from type Book?

A Pick&lt;Book, {id, title}&gt;

B Pick&lt;Book, ['id', 'title']&gt;

C Pick&lt;Book, 'id' | 'title'&gt;

D Pick&lt;Book, id, title&gt;

The keys must be a union of string literals, like 'id' | 'title'.

What error occurs if you pick a property not in the original type?

A Runtime error

B TypeScript error: Type '"wrongKey"' is not assignable to keys of T

C No error, property is ignored

D Warning but code compiles

TypeScript checks keys at compile time and errors if keys don't exist.

Can Pick be used to create a type with all properties optional?

A No, use <code>Partial</code> for that

B Yes, <code>Pick</code> makes properties optional

C Yes, but only for string properties

D No, it removes properties instead

Pick selects properties but does not change optionality; Partial makes properties optional.

Which utility type can be combined with Pick to make picked properties readonly?

A Partial

B Exclude

C Record

D Readonly

Readonly makes properties readonly and can wrap a Pick type.

Explain how the Pick type works and give an example of its syntax.

Think about choosing only some keys from a bigger object type.

Describe a situation where using Pick would make your TypeScript code better.

Imagine you only need a few details from a big object.