TypeScript 2 in action
Александр Русаков / Techops
github.com/arusakov
Немного истории
TypeScript 1.8 22 февраля 2016 г.
TypeScript 2.0 22 сентября 2016 г.
TypeScript 2.1 7 декабря 2016 г.
TypeScript 2.2 RC 2 февраля 2017 г.
blogs.msdn.microsoft.com/typescript/ 2
О чем пойдет речь ● Защита от Undefined / Null● Literal Types и что это такое● Размеченные объединения и Redux● Типизация для React Component API
3
Undefined everywhere
4
Undefined / Null
TypeError: Cannot read property 'x' of undefined
TypeError: Cannot read property 'y' of null
5
Undefined / Null type User = {
name: string
tags?: string[]
}
function getTags(user: User) {
return user.tags.join(', ')
}
6
type User = {
name: string
tags?: string[]
}
function getTags(user: User) {
return user.tags.join(', ')
}
Undefined / Null
7
type User = {
name: string
tags?: string[]
}
function getTags(user: User) {
return user.tags.join(', ')
}
Undefined / Null
8
Non-Nullable Types
https://github.com/Microsoft/TypeScript/pull/7140
// tsc --strictNullChecks
function getTags(user: User) {
return user.tags.join(', ')
}
// ERROR: Object is possibly 'undefined'
9
Non-Nullable Types// tsc --strictNullChecks
function getTagStrict(user: User) {
return user.tags && user.tags.join(', ')
}
10
Non-Null Assertion !// tsc --strictNullChecks
function getTagForce(user: User) {
return user.tags!.join(', ')
}
11
Literal Types
12
???
font-weight
13
Какие допустимые значения этого CSS свойства?
font-weight
14
Какие допустимые значения этого CSS свойства?
initial, inherit, unset,normal, bold, bolder, lighter100, 200, 300, 400, 500, 600, 700, 800, 900
https://www.w3.org/TR/css-fonts-3/#font-weight-prop
font-weight
15
type fontWeight = number | string
<div style={{ fontWeight: 1000 }} />
<div style={{ fontWeight: 'ligther' }} />
font-weight
16
type fontWeight = number | string
<div style={{ fontWeight: 1000 }} />
<div style={{ fontWeight: 'ligther' }} />
font-weight
17
type fontWeight = number | string
<div style={{ fontWeight: 1000 }} />
<div style={{ fontWeight: 'ligther' }} />
Literal Types
18
type fontWeight =
'initial' | 'inherit' | 'unset' |
'normal' | 'bold' | 'bolder' | 'lighter' |
100 | 200 | 300 | 400 | 500 |
600 | 700 | 800 | 900
https://github.com/Microsoft/TypeScript/pull/9407
Literal Types
19
<div style={{ fontWeight: 1000 }} />
<div style={{ fontWeight: 'ligther' }} />
// ERROR: Types of property 'fontWeight' are incompatible.
TypeScript 1 + Reduximport { Action } from 'redux' // Interface
const ACTION_TYPE_1 = 'type1'
interface Action1 extends Action {
data: number
}
20
TypeScript 1 + Reduxfunction reduce(state, action: Action) {
switch (action.type) {
case ACTION_TYPE_1:
action.data
}
}
21
TypeScript 1 + Reduxfunction reduce(state, action: Action) {
switch (action.type) {
case ACTION_TYPE_1:
action.data
}
}
// ERROR: Property 'data' does not exist on type 'Action'
22
TypeScript 1 + Redux
23
function reduce(state, action: Action) {
switch (action.type) {
case ACTION_TYPE_1:
(action as Action1).data // number
}
}
TypeScript 1 + Redux ≠ ♥
24
TypeScript 2
25
Discriminated Union Typestype Action =
{ type: 'type1', id: number } |
{ type: 'type2', name: string }
26https://github.com/Microsoft/TypeScript/pull/9163
Discriminated Union Typesconst ACTION_TYPE1 = 'type1'
const ACTION_TYPE2 = 'type2'
27
Discriminated Union Typesconst ACTION_TYPE1 = 'type1'
const ACTION_TYPE2 = 'type2'
type Action =
{ type: typeof ACTION_TYPE1, id: number } |
{ type: typeof ACTION_TYPE2, name: string }
28
TypeScript 2 ♥ Redux
https://spin.atomicobject.com/2016/09/27/typed-redux-reducers-typescript-2-0/
switch (action.type) {
case ACTION_TYPE1:
action.id // number
case ACTION_TYPE2:
action.name // string
}
29
React
30
TypeScript 1 + Reacttype State = { x: number, y: string }
this.state.x = 1
this.setState({ y: e.target.value })
31
TypeScript 1 + Reacttype State = { x: number, y: string }
this.state.x = 1
this.setState({ y: e.target.value })
// ERROR: Property 'x' is missing
32
TypeScript 1 + Reacttype State = { x: number, y: string }
this.state.x = 1
this.setState({ y: e.target.value } as State)
33
TypeScript 1 + React ≠ ♥
34
Index+Mapped Types// react.d.ts
class Component<P, S> {
setState<K extends keyof S>(s: Pick<S, K>): void;
props: Readonly<P>;
state: Readonly<S>;
}
35
https://github.com/Microsoft/TypeScript/pull/11929
https://github.com/Microsoft/TypeScript/pull/12114
TypeScript 2 ♥ React type State = { x: number, y: string }
this.state.x = 1
// ERROR: Cannot assign because it is a read-only property
this.setState({ y: e.target.value })
36
Predefined Mapped Types// lib.es6.d.ts
Pick<T, K extends keyof T>
Readonly<T>
Partial<T>
Record<K extends string, T>37
В заключение
38
github.com/Microsoft/TypeScript/wiki/What's-new-in-TypeScript
github.com/Microsoft/TypeScript/wiki/Roadmap
Спасибо за вниманиеВопросы?
Презентация и материалы: bit.ly/2kzGfOP
Александр Русаков / Techops
github.com/arusakov
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