if (otherName !== undefined) { this.name = otherName; } } err() { this.name = "not ok"; //Cannot assign to 'name' because it is a read-only property. } } const g = new Greeter(); g.name = "also not ok"; //Cannot assign to 'name' because it is a read-only property...
type 类型别名 // 为某类型指定别名 type Name = string type Age = number type Man = { name: Name age: Age } const c: Man = { name: 'c', age: 20 } keyof 对象键类型 type _Object = { [key: string]: unknown } function getKeysByObj<T extends _Object>(o: T): (keyof T)[]{...
key: 方法名中的Key = PropertyName(普通非Symbol属性) + PropertySymbol(Symbol属性) 如果方法名中包含key,则说明该方法同时遍历普通非Symbol属性以及Symbol属性 如果方法名中包含PropertyNames,则说明该方法只遍历普通非Symbol属性,不遍历Symbol属性 如果方法名中包含PropertySymbols,则说明该方法只遍历Symbol属性,不遍历...
// interface通过extends实现继承 interface userName { name: string; } interface user extends userName { age: number } let stu:user = {name: 'wang', age: 10} // interface的extends扩展可以通过type交叉(&)类型实现 type userName = { name: string; } type user = userName & {age: number} le...
<script lang="ts"setup name="App">//显示注解类型let a: number =1//a 是数字let b:string='hello'//b 是字符串let c: boolean[] = [true,false];//布尔类型数组</script> 如果将 a 写成let a: number = '3',vscode 中 a 就会出现红色波浪,移上去会看到提示:不能将类型“string”分配给类型...
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...
firstName:"Hello", lastName:"TypeScript"}); 这样调用是没有问题的,但是如果传入的参数不是想要的参数格式时,就会出现一些错误: getFullName();//Uncaught TypeError: Cannot destructure property `a` of 'undefined' or 'null'.getFullName({ age: 18, phone: 110 });//'undefined undefined'getFullNam...
get: getter, set: setter, enumerable: true, configurable: true }); } class Person { @logProperty public name: string; constructor(name : string) { this.name = name; } } const p1 = new Person("semlinker"); p1.name = "kakuqo"; ...
getName: (n: number) => { return n; }, }; let t2: TypeItf<string> = { name: "123", getName: (n: string) => { return n; }, }; 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18.
// 错误的调用getUserInfo();// 错误信息:An argument for 'user' was not provided.getUserInfo({name:"coderwhy"});// 错误信息:Property 'age' is missing in type '{ name: string; }'getUserInfo({name:"coderwhy",height:1.88});// 错误信息:类型不匹配 ...