TypeScript 已成为构建可扩展 JavaScript 应用程序的首选语言。在这份综合指南中，我们将探索高级 TypeScript 概念，这些概念将增强您的开发技能并帮助您编写更多类型安全的代码。
理解复杂类型关系：
type IsArray<T> = T extends any[] ? true : false; type IsString<T> = T extends string ? true : false; // Usage type CheckArray = IsArray<string[]>; // true type CheckString = IsString<"hello">; // true // More complex conditional types type UnwrapPromise<T> = T extends Promise<infer U> ? U : T; type ArrayElement<T> = T extends (infer U)[] ? U : never; // Example usage type PromiseString = UnwrapPromise<Promise<string>>; // string type NumberArray = ArrayElement<number[]>; // number
利用字符串文字类型来提高类型安全性：
type HTTPMethod = 'GET' | 'POST' | 'PUT' | 'DELETE';
type APIEndpoint = '/users' | '/posts' | '/comments';
type APIRoute = `${HTTPMethod} ${APIEndpoint}`;
// Valid routes
const validRoute: APIRoute = 'GET /users';
const validRoute2: APIRoute = 'POST /posts';
// Error: Type '"PATCH /users"' is not assignable to type 'APIRoute'
// const invalidRoute: APIRoute = 'PATCH /users';
// Dynamic template literal types
type PropEventType<T extends string> = `on${Capitalize<T>}`;
type ButtonEvents = PropEventType<'click' | 'hover' | 'focus'>;
// Results in: 'onClick' | 'onHover' | 'onFocus'
创建灵活且类型安全的通用接口：
interface Database<T extends { id: string }> {
find(id: string): Promise<T | null>;
create(data: Omit<T, 'id'>): Promise<T>;
update(id: string, data: Partial<T>): Promise<T>;
delete(id: string): Promise<boolean>;
}
// Implementation example
class MongoDatabase<T extends { id: string }> implements Database<T> {
constructor(private collection: string) {}
async find(id: string): Promise<T | null> {
// Implementation
return null;
}
async create(data: Omit<T, 'id'>): Promise<T> {
// Implementation
return { id: 'generated', ...data } as T;
}
async update(id: string, data: Partial<T>): Promise<T> {
// Implementation
return { id, ...data } as T;
}
async delete(id: string): Promise<boolean> {
// Implementation
return true;
}
}
高级类型转换：
type Getters<T> = {
[K in keyof T as `get${Capitalize<string & K>}`]: () => T[K]
};
interface Person {
name: string;
age: number;
}
type PersonGetters = Getters<Person>;
// Results in:
// {
// getName: () => string;
// getAge: () => number;
// }
// Advanced key remapping with filtering
type FilteredKeys<T, U> = {
[K in keyof T as T[K] extends U ? K : never]: T[K]
};
interface Mixed {
name: string;
count: number;
isActive: boolean;
data: object;
}
type StringKeys = FilteredKeys<Mixed, string>;
// Results in: { name: string }
创建强大的元数据驱动的装饰器：
function ValidateProperty(validationFn: (value: any) => boolean) {
return function (target: any, propertyKey: string) {
let value: any;
const getter = function() {
return value;
};
const setter = function(newVal: any) {
if (!validationFn(newVal)) {
throw new Error(`Invalid value for ${propertyKey}`);
}
value = newVal;
};
Object.defineProperty(target, propertyKey, {
get: getter,
set: setter,
enumerable: true,
configurable: true,
});
};
}
class User {
@ValidateProperty((value) => typeof value === 'string' && value.length > 0)
name: string;
@ValidateProperty((value) => typeof value === 'number' && value >= 0)
age: number;
constructor(name: string, age: number) {
this.name = name;
this.age = age;
}
}
构建强大的类型转换：
// Deep Partial type
type DeepPartial<T> = {
[P in keyof T]?: T[P] extends object
? DeepPartial<T[P]>
: T[P];
};
// Deep Required type
type DeepRequired<T> = {
[P in keyof T]-?: T[P] extends object
? DeepRequired<T[P]>
: T[P];
};
// Deep Readonly type
type DeepReadonly<T> = {
readonly [P in keyof T]: T[P] extends object
? DeepReadonly<T[P]>
: T[P];
};
// Example usage
interface Config {
server: {
port: number;
host: string;
options: {
timeout: number;
retries: number;
};
};
database: {
url: string;
name: string;
};
}
type PartialConfig = DeepPartial<Config>;
// Now we can have partial nested objects
const config: PartialConfig = {
server: {
port: 3000
// host and options can be omitted
}
};
实现具有完整类型安全的构建器模式：
class RequestBuilder<T = {}> {
private data: T;
constructor(data: T = {} as T) {
this.data = data;
}
with<K extends string, V>(
key: K,
value: V
): RequestBuilder<T & { [key in K]: V }> {
return new RequestBuilder({
...this.data,
[key]: value,
});
}
build(): T {
return this.data;
}
}
// Usage
const request = new RequestBuilder()
.with('url', 'https://api.example.com')
.with('method', 'GET')
.with('headers', { 'Content-Type': 'application/json' })
.build();
// Type is inferred correctly
type Request = typeof request;
// {
// url: string;
// method: string;
// headers: { 'Content-Type': string };
// }
创建强大的错误处理系统：
class Result<T, E extends Error> {
private constructor(
private value: T | null,
private error: E | null
) {}
static ok<T>(value: T): Result<T, never> {
return new Result(value, null);
}
static err<E extends Error>(error: E): Result<never, E> {
return new Result(null, error);
}
map<U>(fn: (value: T) => U): Result<U, E> {
if (this.value === null) {
return new Result(null, this.error);
}
return new Result(fn(this.value), null);
}
mapError<F extends Error>(fn: (error: E) => F): Result<T, F> {
if (this.error === null) {
return new Result(this.value, null);
}
return new Result(null, fn(this.error));
}
unwrap(): T {
if (this.value === null) {
throw this.error;
}
return this.value;
}
}
// Usage example
function divide(a: number, b: number): Result<number, Error> {
if (b === 0) {
return Result.err(new Error('Division by zero'));
}
return Result.ok(a / b);
}
const result = divide(10, 2)
.map(n => n * 2)
.unwrap(); // 10
这些高级 TypeScript 模式展示了该语言在创建类型安全且可维护的应用程序方面的强大功能。通过掌握这些概念，您将能够更好地构建强大的应用程序，充分利用 TypeScript 的类型系统的潜力。
TypeScript 文档
TypeScript 深入探究
TypeScript GitHub 存储库
在下面的评论中分享您对这些模式的体验！您发现哪些高级 TypeScript 功能在您的项目中最有用？
标签：#typescript #javascript #webdevelopment #programming #typing
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