Set是一种集合类型,它存储唯一的值。 代码语言:txt 复制 let setOfNumbers: Set<number> = new Set([1, 2, 3, 4]); let setOfStrings: Set<string> = new Set(["a", "b", "c"]); 4. 使用Map Map是一种键值对的集合,其中键和值可以是任意类型。
TypeScript 官方手册翻译计划【五】:对象类型 说明:目前网上没有TypeScript最新官方文档的中文翻译,所以有了这么一个翻译计划。因为我也是 TypeScript 的初学者,所以无法保证翻译百分之百准确,若有错误,欢迎评论区指出; 翻译内容:暂定翻译内容为TypeScript Handbook,后续有空会补充翻译文档的其它部分; 项目地址:TypeScrip...
class Base {get foo() {return 100;}set foo() {// ...}}class Derived extends Base {foo = 10;// ~~~// error!// 'foo' is defined as an accessor in class 'Base',// but is overridden here in 'Derived' as an instance property.}class Base {prop = 10;}class Derived extends Ba...
const [count, setCount] = useState<number>(1) 如果初始值为null,需要显式地声明 state 的类型: const [count, setCount] = useState<number |null>(null); 如果state是一个对象,想要初始化一个空对象,可以使用断言来处理: const [user, setUser] = React.useState<IUser>({} as IUser); 实际上,这...
String literal types in TypeScript allow us to model functions and APIs that expect a set of specific strings. Copy function setVerticalAlignment(pos: "top" | "middle" | "bottom") { // ... } setVerticalAlignment("middel"); // ~~~ // error: Argument of type '"middel"' is not assign...
In JavaScript, if an attribute value is not set, we getundefined. So we can deal with it speciallyundefined function paintShape(opts: PaintOptions) { let xPos = opts.xPos === undefined ? 0 : opts.xPos; // let xPos: number
想象一下,如果我们正使用 TypeScript 编写一个库,并将名为 doSTuff 的函数作为公共 API 的一部分进行导出。该函数的 type 声明需要两个 strings,以便其他 TypeScript 用户正常获取 type-checking 错误。但与此同时,它还需要执行运行时检查(可能仅在开发 build 中)以向 JavaScript 用户提示错误信息。
// capture the current state of 'i' // by invoking a function with its current value (function(i) { setTimeout(function() { console.log(i); }, 100 * i); })(i); } 0 1 2 3 4 5 6 7 8 9 let声明 // let声明 let hello = "Hello!"; // 代码块作用域 function f(input: ...
In TypeScript 5.0, we ensured that our Node and Symbol objects had a consistent set of properties with a consistent initialization order. Doing so helps reduce polymorphism in different operations, which allows runtimes to fetch properties more quickly. By making this change, we witnessed impressive...
* Construct a type with a set of properties K of type T */ type Record<K extends string, T> = { [P in K]: T }; 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 这里还有两个关于映射类型的例子,如果需要的话,可以自己编写: ...