constmyArray:StringArray= ["Alice","Bob"]; console.log(myArray[0]);// "Alice" 混合索引签名 interfaceUserDictionary{
Retrieve by indexIterate throughUse map/filter/reduceUse forEachCreate array from SetRetrieve value by keyUse a Map for key-value pairsArrayIndexAccessLoopingHigherOrderFunctionSetConvertToArrayDictionaryAccessByKeyMapUsage 5.2 类图 以下是一个类图,展示了集合对象的基本结构: Array+getElement(index: number...
function createArray<T>(length: number, value: T): Array<T> { let result: T[] = []; for (let i = 0; i < length; i++) { result[i] = value; } return result; } //函数名后添加了 <T>,其中 T 用来指代任意输入的类型,在后面的输入 value: T 和输出 Array<T> 中即可使用了。
let myArray: StringArray; myArray= ["Bob", "Fred"]; let myStr: string= myArray[0];//定义的StringArray接口,它具有索引签名,表示当用number去索引StringArray时会得到string类型的返回值。interface NumberDictionary { [index: string]: number; length: number;//可以,length是number类型name: string//...
function identity<T>(arg: Array<T>): Array<T> { console.log(arg.length); return arg; } 4.2 检查对象上的键是否存在 泛型约束的另一个常见的使用场景就是检查对象上的键是否存在。不过在看具体示例之前,我们得来了解一下keyof操作符,keyof操作符是在 TypeScript 2.1 版本引入的,该操作符可以用于获取某种...
interface NumberOrStringDictionary { [index: string]: number | string; length: number; // ok, length is a number name: string; // ok, name is a string }Try Finally, you can make index signatures readonly in order to prevent assignment to their indices: interface ReadonlyStringArray { ...
Tuples become very useful when we want to create a dictionary or a key-value pair. Using our example from above, we can have an array of user names and their ids without mistakenly passing in a different type to create problems later. ...
(val: string) => void // 另一种方法声明 (): { name: string } // 调用签名 new (): { name: string } // 构造函数签名 [prop: string]: string; // 索引签名属性,key 支持 string, number, symbol } // 数组通过泛型和索引签名属性定义 interface Array<T> { length: number; toString():...
console.log(arrayLength([1, 2, 3])); // 输出: 3 接口与类的混合类型 在TypeScript中,你可以在接口中定义类的静态属性和实例属性,这使得接口可以描述类的完整形状。 示例:接口与类的混合类型 interface ClockInterface { currentTime: Date; tick(): void; ...
For instance, let’s borrow our industrial strength string-padder example from earlier:interface Padder { getPaddingString(): string; } class SpaceRepeatingPadder implements Padder { constructor(private numSpaces: number) {} getPaddingString() { return Array(this.numSpaces + 1).join(" "); } ...