2024-05-06 20:40:05 +00:00
|
|
|
---
|
2024-10-30 17:34:11 +00:00
|
|
|
date: 2020-10-09
|
2024-05-06 20:40:05 +00:00
|
|
|
id: b6fa7fa7-644f-42ab-bee6-71f4f58a60f2
|
|
|
|
|
title: TypeScript Classes
|
|
|
|
|
---
|
|
|
|
|
|
|
|
|
|
# TypeScript 4.0
|
|
|
|
|
|
|
|
|
|
## Class Property Inference from Constructors
|
|
|
|
|
|
|
|
|
|
TypeScript 4.0 can now use control flow analysis to determine the types
|
|
|
|
|
of properties in [classes](20201008090316-class_notation) when
|
|
|
|
|
noImplicitAny is enabled.
|
|
|
|
|
|
|
|
|
|
``` typescript
|
|
|
|
|
class Square {
|
|
|
|
|
// Previously: implicit any!
|
|
|
|
|
// Now: inferred to `number`!
|
|
|
|
|
area;
|
|
|
|
|
sideLength;
|
|
|
|
|
|
|
|
|
|
constructor(sideLength: number) {
|
|
|
|
|
this.sideLength = sideLength;
|
|
|
|
|
this.area = sideLength ** 2;
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
```
|
