How structural typing differs from nominal typing in Typescript - Quick Revision & Summary

Recall & Review

beginner

What is structural typing?

Structural typing means that two types are compatible if their shapes (properties and methods) match, regardless of their names.

beginner

What is nominal typing?

Nominal typing means that two types are compatible only if they have the same name or explicitly declared relationship, regardless of their structure.

beginner

How does TypeScript use typing?

TypeScript uses structural typing, so it checks if types have matching properties and methods rather than relying on type names.

intermediate

Example: Why are two objects with the same properties compatible in structural typing?

Because structural typing compares the shape (properties and methods), two objects with the same shape are considered the same type even if their names differ.

intermediate

Why might nominal typing be preferred in some languages?

Nominal typing helps catch errors by requiring explicit type relationships, making sure only intended types are compatible, which can improve safety.

In structural typing, two types are compatible if:

A They have the same shape (properties and methods).

B They have the same name.

C They are declared in the same file.

D They have different properties.

Structural typing checks if the shapes match, not the names.

Which typing system requires explicit type names to match for compatibility?

A Structural typing

B Dynamic typing

C Duck typing

D Nominal typing

Nominal typing requires type names or explicit declarations to match.

TypeScript primarily uses which typing system?

A Nominal typing

B Dynamic typing

C Structural typing

D Duck typing

TypeScript uses structural typing to check type compatibility.

If two objects have the same properties but different names, are they compatible in TypeScript?

A No, because names must match.

B Yes, because TypeScript uses structural typing.

C Only if explicitly declared.

D Only if they are classes.

TypeScript compares object shapes, so names don't matter.

Which typing system can help prevent accidental type compatibility?

A Nominal typing

B Structural typing

C Duck typing

D Dynamic typing

Nominal typing requires explicit type matches, reducing accidental compatibility.

Explain in your own words how structural typing differs from nominal typing.

Think about whether type names or properties matter more.

Why might a language choose nominal typing over structural typing?

Consider how strict the type system should be.