functiontest(a:number,b:number){returna+b;}typeA=ReturnType<typeoftest>; A 就是 number 类型。也就是 Typescript 知道两个 number 相加结果也是一个 number。因此即使你不显示地注明返回值是 number, Typescript 也能猜到。「这也是为什么 JavaScript 项目不接入 Typescript 也可以获得类型提示的原因之一」。
AI代码解释 classdanli{//先声明一个存单例要用的变量privatestaticdanli:danlistaticgetDanli(){//判断是否有单例了if(!this.danli){this.danli=newdanli()}//返回returnthis.danli;}test(){console.log(this)}}consta1=danli.getDanli()consta2=danli.getDanli()复制代码 7、抽象类 抽象类做为其它派生类的...
function test(a:number|undefined):string{if(a===undefined){return'';}return a.toString();}test();//TS2554:Expected1arguments,but got0. test(undefined); 1. 2. 3. 4. 5. 6. 7. 8. 之所以会报错是因为在 ts 中,undefined 是一个特殊的类型,由于类型为 undefined,并不代表可 缺省,因此示例...
interfaceTestInterface{ name:string, age:number }//我们可以通过+/-来指定添加还是删除//把上面定义的接口里面的属性全部变成可选type OptionalTestInterface<T> ={ [pinkeyof T]+?:T[p] }//再加上只读type OptionalTestInterface<T> ={+readonly[pinkeyof T]+?:T[p] } type newTestInterface= Optiona...
b?:string;// 可选属性readonlyc:number;// 只读属性[key:number]:string;// 索引类型}// 接口继承interfaceIbextendsIa{age:number; }lettest1:Ia= {a:"",c:2,age:1, }; test1.c=2;// 报错,只读属性constitem0 = test1[0];// 索引类型 ...
import{Component,Prop,Vue,Watch}from'vue-property-decorator';@ComponentexportdefaultclassTestextendsVue{privatename:string;} Prop 声明 代码语言:javascript 代码运行次数:0 运行 AI代码解释 @Prop({default:false})privateisCollapse!:boolean;@Prop({default:true})privateisFirstLevel!:boolean;@Prop({default:...
a: number =1 b: number =2 c: number =3 d: number =4 name:string='name' test(){ console.log('this is test') } } classCarProxy{ privatecar:Car name: number constructor(){ if(this.car ===null){ this.car =newCar } this.name =this.car.name ...
"scripts": { "start": "tsc && node --unhandled-rejections=strict ./dist/app.js", "debug": "export DEBUG=* && npm run start", "test": "echo \"Error: no test specified\" && exit 1" }, The test script is a placeholder that we’ll replace later in the series. The tsc in ...
functionuppercaseStrings(x:string| number) {if(typeofx==="string") {// TypeScript knows 'x' is a 'string' here.returnx.toUpperCase(); } } One common pain-point was that these narrowed types weren’t always preserved within function closures. ...
protected num: number; constructor(num: number) { this.num = num } } class B extends A { test() { console.log(this.num); } } const b = new B(345) b.num = 22 // 报错 属性“num”受保护,只能在类“A”及其子类中访问 1. ...