bashANYtypescripttsctsconfigsetup
bash
npx tsc --initGenerates a starter `tsconfig.json` file with common compiler options.
TypeScript Cheat Sheet
Core TypeScript syntax, typing patterns, and compiler commands.
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Setup and CLI
Project setup, compiler usage, and quick inspection.
bashANYtypescripttscversion
bash
npx tsc --versionUseful when debugging behavior differences across TypeScript releases.
bashANYtypescripttsctypecheckci
bash
npx tsc --noEmitCommon CI command for catching errors without writing build output.
bashANYtypescripttscwatch
bash
npx tsc --watchKeeps the compiler running and recompiles on file changes.
bashANYtypescripttsctsconfigproject
bash
npx tsc -p tsconfig.jsonPass `-p` or `--project` to point TypeScript at a specific config file or directory.
bashANYtypescripttscbuildproject-references
bash
npx tsc --buildBuild mode is intended for composite projects and project references.
bashANYtypescripttscdebuggingfiles
bash
npx tsc --explainFilesUseful for debugging include/exclude and file graph issues.
bashANYtypescripttscmodule-resolutiondebugging
bash
npx tsc --traceResolutionUseful when path aliases or package resolution behave unexpectedly.
Primitive Types and Annotations
Basic types, annotations, inference, and literal behavior.
typescriptANYtypescriptprimitivesannotations
typescript
const appName: string = "CheatSheet";
const port: number = 3000;
const isProd: boolean = false;Type annotations are optional in many cases because TypeScript can infer them.
typescriptANYtypescriptarraysannotations
typescript
const ids: number[] = [1, 2, 3];
const names: Array<string> = ["Ada", "Linus"];Both array syntaxes are common; choose one style and stay consistent.
typescriptANYtypescriptobjectsannotations
typescript
const user: { id: number; name: string; admin?: boolean } = {
id: 1,
name: "Ada"
};Optional properties use `?` in object type annotations.
typescriptANYtypescriptunions
typescript
let value: string | number;
value = "ok";
value = 42;Union types are one of the most common TypeScript patterns.
typescriptANYtypescriptliteral-typesunions
typescript
type Theme = "light" | "dark" | "system";
const theme: Theme = "dark";Literal unions are ideal for config values, modes, and command flags.
typescriptANYtypescriptinference
typescript
const count = 10; // number
const title = "Hello"; // stringInference usually produces cleaner code than over-annotating every value.
typescriptANYtypescriptas-constliteral-types
typescript
const statusMap = {
ok: 200,
notFound: 404,
} as const;`as const` narrows values to their literal types and makes properties readonly.
Objects, Interfaces, and Type Aliases
Reusable object shapes and composition patterns.
typescriptANYtypescriptinterfaceobjects
typescript
interface User {
id: number;
name: string;
email?: string;
}Interfaces are commonly used for object shapes, especially public APIs.
typescriptANYtypescripttype-alias
typescript
type UserId = string | number;
type Point = { x: number; y: number };Type aliases are more flexible than interfaces for unions and mapped types.
typescriptANYtypescriptinterfaceextends
typescript
interface Person {
name: string;
}
interface Employee extends Person {
team: string;
}`extends` helps model shared fields without duplication.
typescriptANYtypescriptintersection-types
typescript
type Audit = { createdAt: Date };
type Customer = { id: string; name: string };
type AuditedCustomer = Customer & Audit;Intersection types are useful when enriching objects with shared metadata.
typescriptANYtypescriptreadonly
typescript
type Config = {
readonly apiBaseUrl: string;
readonly retries: number;
};Readonly protects values from reassignment after initialization.
typescriptANYtypescriptindex-signatureobjects
typescript
type StringMap = {
[key: string]: string;
};Index signatures are useful for config maps and lookup tables.
Tuples and Enums
Position-based arrays and enum patterns.
typescriptANYtypescripttuples
typescript
const point: [number, number] = [10, 20];Tuples are useful when position matters and object keys would be excessive.
typescriptANYtypescripttuples
typescript
type HttpResponse = [status: number, body: string];Tuple labels improve editor help without changing runtime behavior.
typescriptANYtypescriptenum
typescript
enum Direction {
Up,
Down,
Left,
Right,
}Enums exist in TypeScript, though many teams prefer literal unions for simpler output.
typescriptANYtypescriptenumstring-enum
typescript
enum Status {
Draft = "draft",
Published = "published",
}String enums are easier to debug than numeric enums in serialized output.
More in TypeScript
TypeScript Utility Types and Recipes
Built-in utility types and practical application patterns.
TypeScript tsconfig and Tooling
tsconfig.json patterns, diagnostics, and project references.
TypeScript Classes and Modules
Classes, access modifiers, inheritance, modules, and validation boundaries.
TypeScript Functions and Narrowing
Function typing, overloads, control-flow narrowing, and async typing.
TypeScript Types and Generics
Advanced type operators, mapped types, conditional types, and utility types.