plot({ x: 10, y: 25 }); // Okay. plot({ x: 8, y: 13, name: 'foo' }); // Extra fields Okay. Need enable `suppressExcessPropertyError` 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 细细品味,当真没有一点违和感。理想中的 JavaScript 类型系统就应该是这样。 另外一个好处稍稍隐晦...
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...
type Foo = number | { someProperty: number } 当你需要继承或实现时,使用 interface 代码语言:javascript 代码运行次数:0 运行 AI代码解释 interface Foo { foo: string; } interface FooBar extends Foo { bar: string; } class X implements FooBar { foo: string; bar: string; } 风格指南 使用箭头函...
Property 'breeds' is missing in type 'Animal' but required in type 'Dog'.</pre> 1. 2. 3. 这里,getAnimalName 是比 getDogName 更广泛的函数。因此,在这种情况下,无法将超类型分配给子类型。但是,可以将子类型分配给超类型。大多数时候,函数参数应该是逆变的,而不是双向协变的。如果启用这个编译选项...
}for(let idinsecond) {if(!result.hasOwnProperty(id)) { (<any>result)[id] = (<any>second)[id]; } }returnresult; }/** * 联合类型*/interface Fish{ swim(); layEggs(); } interface Bird{ fly(); layEggs(); }functiongetSmallPet():Fish |Bird{//...} let...
{// Proxy - 代理(拦截目标对象的属性操作和函数操作)lettarget = {name:'webabcd',age:40,gethello() {returnthis.name+this.age; } }lethandler = {get:function(target:any, propertyKey:string, receiver:any) {// receiver 就是 Proxy 实例本身console.log("get: "+ propertyKey);returntarget[prop...
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,...
(); }; // 替换属性,先删除原先的属性,再重新定义属性 if (delete target[propertyKey]) { Object.defineProperty(target, propertyKey, { get: getter, set: setter, enumerable: true, configurable: true, }); } } class Person { @upperCase name!: string; } let p: Person = new Person(); p...
instanceof类型保护如果你已经阅读了typeof类型保护并且对JavaScript里的instanceof操作符熟悉的话,你可能已经猜到了这节要讲的内容。instanceof类型保护是通过构造函数来细化类型的一种方式。比如,我们借鉴一下之前字符串填充的例子:interface Padder { getPaddingString(): string } class SpaceRepeatingPadder implements...
function appendUrlParams(url: string | URL, params: Record<string, number>) { if (typeof url === 'string') { url = new URL(url); } Object.entries(params).forEach(([param, value]) => { // Property 'searchParams' does not exist on type 'string | URL'. error before 5.4, now...