log("数字是正数"); }else if(num = 0){ console.log("数字是0"); }else{ console.log("数字是负数"); } } getNum(-1); TypeScript中的参数。 TypeScript中的参数分为正常参数,可选参数,剩余参数。 正常参数,方法在定义时需要几个参数就定义几个参数,调用时也需要上送对用的参数个数和参数类型。
functionbound(originalMethod:any,context:ClassMethodDecoratorContext){constmethodName=context.name;if(context.private){thrownewError(`'bound' cannot decorate private properties like${methodNameasstring}.`);}context.addInitializer(function(){this[methodName]=this[methodName].bind(this);});} bound不会...
typeof undeclaredVariable === 'undefined'; typeof null === 'object'; typeof false === 'boolean'; typeof Boolean(1) === 'boolean'; // Boolean() 会基于参数是真值还是虚值进行转换 // Symbols typeof Symbol() === 'symbol'; typeof Symbol('foo') === 'symbol'; typeof Symbol.iterato...
interface Checkable { check(name: string): boolean; } class NameChecker implements Checkable { check(s) { // Parameter 's' implicitly has an 'any' type. // Notice no error here return s.toLowercse() === "ok"; // any } } 在这个例子中,我们可能预计s的类型会受到check的name: string...
//打开 exactOptionalPropertyTypesinterfaceMyObj { foo?:'A'|'B'; } let obj:MyObj= { foo:'A'}; obj.foo= undefined;//报错 上面示例中,foo是可选属性,打开exactOptionalPropertyTypes以后,该属性就不能显式赋值为undefined。 16. forceConsistentCasingInFileNames ...
接口是用关键字定义的interface,它可以包含使用函数或箭头函数的属性和方法声明。 interfaceIEmployee {empCode:number;empName:string;getSalary:(number) =>number;// arrow functiongetManagerName(number):string;} 6、TypeScript 中的模块是什么? TypeScript 中的模块是相...
interface SquareConfig { color?: string; width?: number; } function createSquare(config: SquareConfig): {color: string; area: number} { var newSquare = {color: "white", area: 100}; if (config.color) { newSquare.color = config.collor; // Type-checker can catch the mistyped name her...
type MyInstance = InstanceType<typeof Shape>; That’s why TypeScript 4.2 allows you to specify an abstract modifier on constructor signatures. Copy interface HasArea { getArea(): number; } // Works! let Ctor: abstract new () => HasArea = Shape; // ^^^ Adding the abstract modifier to...
exportinterfaceFoo{number:number;boolean:boolean;maybeString?:string;bar:Bar;}interfaceBar{numbers:number[];} With strict mode functionsanitizeFoo(checker:any){if(typeofchecker.number!="number"||typeofchecker.boolean!="boolean"||(checker.maybeString!=undefined&&typeofchecker.maybeString!="string")...
If it does, the tested value on the left side of the instanceof operator will be narrowed appropriately by that type predicate. Copy interface PointLike { x: number; y: number; } class Point implements PointLike { x: number; y: number; constructor(x: number, y: number) { this.x =...