Helaian Rujukan TypeScript
Rujukan TypeScript yang boleh dicari dan dicetak: jenis, interface, generics, jenis utiliti, narrowing, fail deklarasi dan tsconfig. Percuma.
Basic types
14let name: string = "Ada";
String type annotation
let age: number = 30;
Number (int and float)
let ok: boolean = true;
Boolean
let ids: number[] = [1, 2];
Array of numbers
let pair: [string, number] = ["a", 1];
Tuple: fixed-length typed array
let anything: unknown;
Safe any: must narrow before use
let loose: any;
Opts out of checking (avoid)
function log(): void {}
No return value
function fail(): never { throw new Error(); }
Never returns
let big: bigint = 9007199254740993n;
Arbitrary-precision integer
let id: string | null = null;
Nullable via union
const point = { x: 1 } as const;
Deep readonly literal types
enum Status { Active, Inactive }
Numeric enum
type Dir = "up" | "down";
String literal union (enum-lite)
Interfaces & type aliases
12interface User { id: number; name: string; }
Object shape contract
type User = { id: number; name: string };
Type alias for a shape
interface User { nickname?: string; }
Optional property
interface User { readonly id: number; }
Property cannot be reassigned
interface Admin extends User { role: string; }
Interface inheritance
type Admin = User & { role: string };
Extend an alias via intersection
interface Dict { [key: string]: number; }
Index signature
interface Fn { (x: number): string; }
Callable interface
interface User { greet(): void; }
Method signature
interface Box<T> { value: T; }
Generic interface
interface Window { myGlobal: string; }
Declaration merging (augment)
type Point = Readonly<{ x: number }>;
Readonly wrapper on an alias
Unions, intersections & narrowing
12type Id = string | number;
Union: one of several types
type Full = A & B;
Intersection: all members of both
if (typeof id === "string") { ... }
typeof narrowing
if (el instanceof HTMLElement) { ... }
instanceof narrowing
if ("radius" in shape) { ... }
in-operator narrowing
if (value != null) { ... }
Strip null AND undefined
switch (shape.kind) { case "circle": ... }
Discriminated union switch
type Shape = Circle | Square;
Discriminated union (kind field)
const x = cond ? a : b;
Result type is a union of both
user?.address?.city
Optional chaining
const name = input ?? "default";
Nullish coalescing
function assertNever(x: never): never { throw x; }
Exhaustiveness check helper
Generics
11function first<T>(arr: T[]): T { return arr[0]; }
Generic function
first<string>(["a", "b"])
Explicit type argument
interface Box<T> { value: T; }
Generic interface
class Stack<T> { items: T[] = []; }
Generic class
type Pair<K, V> = { key: K; value: V };
Generic type alias
<T extends { id: number }>
Constrain the type parameter
<T, K extends keyof T>(obj: T, key: K): T[K]
Typed property access
<T = string>
Default type parameter
function wrap<const T>(v: T): T[]
const modifier keeps literals
type Flatten<T> = T extends Array<infer U> ? U : T;
Extract inner type with infer
const map = new Map<string, User>();
Generic built-in collections
Utility types
14Partial<User>
All properties optional
Required<User>
All properties required
Readonly<User>
All properties readonly
Pick<User, "id" | "name">
Keep only the listed keys
Omit<User, "password">
Drop the listed keys
Record<string, number>
Object map of key to value type
Exclude<T, U>
Remove U members from union T
Extract<T, U>
Keep only U members of union T
NonNullable<T>
Strip null and undefined
ReturnType<typeof fn>
Type a function returns
Parameters<typeof fn>
Tuple of a function's params
Awaited<Promise<string>>
Unwrap promise type → string
InstanceType<typeof MyClass>
Instance type from a class
Uppercase<"id"> / Capitalize<"id">
String-literal case transforms
Functions & overloads
11function add(a: number, b: number): number
Typed parameters and return
const add = (a: number, b: number) => a + b;
Arrow function (return inferred)
function log(msg: string, level?: string)
Optional parameter
function log(msg: string, level = "info")
Default parameter value
function sum(...nums: number[]): number
Rest parameters
type Handler = (e: Event) => void;
Function type alias
function get(id: number): User;
function get(ids: number[]): User[];
function get(x: any): any { ... }
Overload signatures + one impl
function fn(this: HTMLElement, e: Event)
Typed this parameter
async function load(): Promise<User>
Async returns a Promise
function isUser(x: unknown): x is User
Type predicate return
const fn: typeof otherFn = ...;
Reuse another function's type
Classes
12class User { constructor(public name: string) {} }
Parameter property shorthand
private secret: string;
Compile-time private member
#secret: string;
Runtime private field (ES)
protected id: number;
Visible to subclasses only
readonly createdAt = new Date();
Assign once, in ctor only
static create(): User { return new User(); }
Static factory method
class Admin extends User { ... }
Inheritance (use super())
class Api implements Fetcher { ... }
Implement an interface
abstract class Shape { abstract area(): number; }
Abstract base class
get fullName(): string { return ...; }
Getter accessor
override toString(): string { ... }
Explicit override (safer)
declare id: number;
Declare without initializing
Type guards & assertions
11function isUser(x: unknown): x is User
Custom type guard
function assertUser(x: unknown): asserts x is User
Assertion function
function assertOk(x: unknown): asserts x
Assert truthy (non-null after)
const el = input as HTMLInputElement;
Type assertion (cast)
value!
Non-null assertion (careful!)
x as unknown as Y
Double assertion (last resort)
const roles = ["admin", "user"] as const;
Literal tuple via const assert
if (Array.isArray(value)) { ... }
Built-in array guard
satisfies Record<string, string>
Check shape, keep inference
typeof x === "object" && x !== null
Safe object check (null trap)
catch (e) { if (e instanceof Error) ... }
Narrow the unknown catch var
Mapped & conditional types
12type Flags<T> = { [K in keyof T]: boolean };
Mapped type over keys
{ [K in keyof T]?: T[K] }
Add ? modifier (Partial)
{ [K in keyof T]-?: T[K] }
Remove ? modifier (Required)
{ readonly [K in keyof T]: T[K] }
Add readonly to all keys
{ -readonly [K in keyof T]: T[K] }
Strip readonly (Mutable)
{ [K in keyof T as `get${Capitalize<string & K>}`]: () => T[K] }
Key remapping with as
type IsString<T> = T extends string ? true : false;
Conditional type
T extends (infer U)[] ? U : never
infer inside a conditional
type Keys = keyof User;
Union of property names
type Value = User["name"];
Indexed access type
type Route = `/users/${number}`;
Template literal type
T extends any ? T[] : never
Distribute over union members
Modules & declaration files
12export interface User { ... }
Named export
export default class Api { ... }
Default export
import { User } from "./user";
Named import
import type { User } from "./user";
Type-only import (erased)
export type { User };
Type-only re-export
import * as path from "node:path";
Namespace import
declare module "my-lib" { ... }
Type an untyped package
declare global { interface Window { ... } }
Augment global scope
declare const VERSION: string;
Ambient declaration (.d.ts)
export {};
Force a file to be a module
/// <reference types="node" />
Triple-slash type reference
npm i -D @types/lodash
Install community typings
tsconfig essentials
13"strict": true
Enable all strict checks (do it)
"target": "ES2022"
Output JavaScript version
"module": "ESNext"
Emitted module system
"moduleResolution": "bundler"
Resolution for Vite/esbuild
"noEmit": true
Type-check only, no output
"esModuleInterop": true
Smooth CommonJS default imports
"skipLibCheck": true
Skip checking .d.ts files
"noUncheckedIndexedAccess": true
arr[i] becomes T | undefined
"paths": { "@/*": ["./src/*"] }
Import path aliases
"outDir": "./dist", "rootDir": "./src"
Output / source directories
"sourceMap": true, "declaration": true
Emit .map and .d.ts files
npx tsc --noEmit
CI type-check command
npx tsc --init
Generate a tsconfig.json
Tiada entri sepadan dengan “:q”.
Mengenai Helaian Rujukan TypeScript
Helaian rujukan TypeScript ini menjadikan sistem jenisnya satu halaman yang boleh dicari: jenis asas, interface dan alias jenis, union, intersection dan narrowing, generics, jenis utiliti terbina dalam, fungsi dan overload, kelas, penjaga jenis dan assertion, jenis mapped dan conditional, modul dan fail deklarasi, serta pilihan tsconfig yang benar-benar penting.
Ia ditulis untuk kerja harian: bentuk tepat kekangan generik, apa fungsi Pick, Omit, Record dan ReturnType, cara discriminated union melakukan narrowing, bila hendak menggunakan `satisfies` dan bukannya cast, supaya anda boleh menyemak sesuatu perincian tanpa meninggalkan editor anda untuk merujuk handbook.
Seperti setiap helaian rujukan dalam kumpulan ini, ia percuma dan di sisi klien: tapis baris secara langsung dengan kotak carian, lompat antara bahagian dengan senarai kandungan yang melekat, salin sebarang cebisan kod dengan satu klik dan cetak halaman untuk rujukan di meja anda.
Cara menggunakan Helaian Rujukan TypeScript
- Buka helaian itu dan imbas bahagiannya, dari Basic types dan Generics hingga ke tsconfig essentials.
- Cari kata kunci seperti Partial, narrowing atau satisfies untuk menapis setiap baris secara langsung.
- Lompat ke Utility types atau Mapped & conditional types apabila anda memerlukan sintaks peringkat jenis yang lebih maju.
- Klik sesuatu cebisan kod atau ikon salinnya untuk menyalin kod TypeScript itu ke papan keratan anda.
- Gunakan Print untuk salinan bercetak bagi keseluruhan rujukan TypeScript.
Soalan lazim
Sebelas bahagian: jenis asas, interface dan alias jenis, union dan narrowing, generics, jenis utiliti, fungsi dan overload, kelas, penjaga jenis dan assertion, jenis mapped dan conditional, modul dan fail deklarasi, serta tsconfig essentials.
Ya. Satu bahagian khusus merangkumi Partial, Required, Readonly, Pick, Omit, Record, Exclude, Extract, ReturnType, Awaited dan selebihnya, setiap satu dengan penjelasan satu baris.
Sangat berguna. Bahagian berasingan menunjukkan narrowing typeof dan instanceof, discriminated union, predikat jenis yang ditakrif pengguna, fungsi assertion dan perbezaan antara cast dengan `satisfies`.
Ya. Klik kod pada mana-mana baris atau ikon salinnya dan ia terus disalin ke papan keratan anda.
Ya, ia sepenuhnya percuma dan berjalan dalam pelayar anda tanpa log masuk.
Carian popular
typescript cheat sheet
typescript types
typescript utility types
typescript generics
typescript interface vs type
tsconfig options
typescript reference
Perlukan bantuan?
Menemui masalah dengan alat ini? Beritahu pasukan kami.