interface Hero { // Hero 接口 id: number; name: string; } getHeroes(): Observable<Hero[]> { return Observable.of([ { id: 1, name: 'Windstorm' }, { id: 13, name: 'Bombasto' }, { id: 15, name: 'Magneta' }, { id: 20, name: 'Tornado' } ]); } 上面getHeroes(): Obse...
typeReadonlyObject<T>={readonly[PinkeyofT]:T[P];};constobj:ReadonlyObject<{name:string;age:number}>={name:"Alice",age:20,};obj.name="Bob";// Error: Cannot assign to 'name' because it is a read-only property. 类型守卫 类型守卫是 TypeScript 中一种用于缩小类型范围的机制。通过使用类...
name: string; age: number; getName: () => void; } class Male implements Person { constructor(name: string, age: number) { = name; this.age = age; } name: string; age: number; getName(): void { console.log(); } } 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. ...
getFullName();//Uncaught TypeError: Cannot destructure property `a` of 'undefined' or 'null'.getFullName({ age: 18, phone: 110 });//'undefined undefined'getFullName({ firstName: "Hello" });//'Hello undefined' 这些都是我们不想要的,在开发时难免会传入错误的参数,所以 TypeScript 能够在编...
semlinker.#name; // ~~~ // Property '#name' is not accessible outside class 'Person' // because it has a private identifier. 与常规属性(甚至使用private修饰符声明的属性)不同,私有字段要牢记以下规则: 私有字段以#字符开头,有时我们称之为私有名称; 每个...
// 错误的调用getUserInfo()// Uncaught TypeError: Cannot read property 'name' of undefinedconsole.log(getUserInfo({name:"kaola"}))// name: kaola, age: undefinedgetUserInfo({name:"kaola",height:1.66})// name: koala, age: undefined
error(getNameOfDeclaration(source.declarations[0]), Diagnostics.Cannot_augment_module_0_with_value_exports_because_it_resolves_to_a_non_module_entity, symbolToString(target)); } else { const message = target.flags & SymbolFlags.BlockScopedVariable || source.flags & SymbolFlags.BlockScopedVariable...
type LowercaseGreeting = "hello, world"; type Greeting = Capitalize<LowercaseGreeting>; // 相当于 type Greeting = "Hello, world" Uncapitalize<StringType>:将字符串首字母转为小写格式 type UppercaseGreeting = "HELLO WORLD"; type UncomfortableGreeting = Uncapitalize<UppercaseGreeting>; // 相当于 typ...
type Name = string; type NameResolver = () => string; type NameOrResolver = Name | NameResolver; function getName(n: NameOrResolver): Name { if (typeof n === 'string') { return n; } else { return n(); } } 起别名不会新建一个类型 - 它创建了一个新名字来引用那个类型。给原始...
functiongetUrls(url: string | URL, names: string[]){if(typeofurl==="string") {url=newURL(url); }returnnames.map(name => {url.searchParams.set("name", name)// ~~~// error!// Property 'searchParams' does not exist on type 'string | URL'.returnurl.toString(); }); } Here,...