name: string; age: number; } letpeople: Person[] = [ { name:"Alice", age: 20 }, { name:"Bob", age: 30 }, ]; 在这个例子中,Person[]是一个对象数组类型,它包含的元素都是Person类型的对象。每个Person类型的对象都有name和age两个属性,类型分别为string和number。 1.3、简单数组类型和泛型数...
It is designed to add type safety to JavaScript while conforming as closely as possible to the syntax and semantics of the ECMAScript standard. It is a syntactical superset of the JavaScript programming language; all valid JavaScript source code is also valid TypeScript source code, but not ...
functionprintId(id:number|string){if(typeofid==="string"){// 在这个分支中,id 的类型是 stringconsole.log(id.toUpperCase());}else{// 这里,id 的类型是 numberconsole.log(id);}} 另一个例子是使用类似Array.isArray这样的函数: 代码语言:javascript 复制 functionwelcomePeople(x:string[]|string){...
type Point={x:number;y:number;};//和之前相似的例子functionprintCoord(pt:Point){console.log("The coordinate's x value is "+pt.x);console.log("The coordinate's y value is "+pt.y);}printCoord({x:100,y:100}); 我们可以将联合类型的例子改造一下: 代码语言:javascript 复制 type Age=stri...
function fn(): undefined { // ts(2355) A function whose declared type is neither 'void' nor 'any' must return a value // TODO } void 类型来表示函数没有返回值的类型，示例如下：function fn1(): void { } fn1().doSomething(); // ts(2339) Property 'doSomething' does not exist on ...
We use a bot to let a large number of pull requests to DefinitelyTyped be handled entirely in a self-service manner. You can read more about why and how here. Here is a handy reference showing the life cycle of a pull request to DT: Edit an existing package Make changes. Remember to...
// Equivalent to: type PickUser = { id: number; age: number; }typePickUser = Pick<User,"id"|"age"> 这些类型内置在 Typescript 中。 3.条件类型 它类似于 ?: 运算符,你可以使用它来扩展一些基本类型。 TextendsU ? X : Y typeisTrue<T> = Text...
interface ICustomerShort { Id: number; CalculateDiscount( discountAmount: ( discountClass: string, multipleDiscount: boolean ) => number): number } That parameter is defined using a function type that accepts two parameters (one of string, one of boolean) and returns a number. If you’re a...
let someValue: any = "this is a string"; let strLength: number = (<string>someValue).length; 3.2 as 语法 let someValue: any = "this is a string"; let strLength: number = (someValue as string).length; 四、类型守卫
constcopy = (value:string|number):string|number=>value // 只能传入 string 或者 numbercopy(10) // 会报错:Argument of type 'boolean' is not assignable to parameter of type 'string | number'// copy(false) 也可以判断 T 是否可以赋值给 U,可以的话返回 T,...