在 TypeScript 中,Map 也可以被视为一种对象类型,并且可以使用 for…in 循环来遍历其键。 下面是一个使用 for…in 循环遍历 Map 键的示例代码: constmap=newMap<number,string>();map.set(1,"one");map.set(2,"two");map.set(3,"three");for(constkeyinmap){if(map.hasOwnProperty(key)){console...
map.has() – 返回一个布尔值,用于判断 Map 中是否包含键对应的值。 map.delete() – 删除 Map 中的元素,删除成功返回 true,失败返回 false。 map.size – 返回 Map 对象键/值对的数量。 map.keys() - 返回一个 Iterator 对象, 包含了 Map 对象中每个元素的键 。 map.values() – 返回一个新的Iter...
functionLog(target:Function,key:string,parameterIndex:number){letfunctionLogged=key||target.prototype.constructor.name;console.log(`The parameter in position${parameterIndex}at${functionLogged}has been decorated`);}classGreeter{greeting:string;constructor(@Log phrase:string){this.greeting=phrase;}}// c...
Map.groupByis similar, but produces aMapinstead of a plain object. This might be more desirable if you need the guarantees ofMaps, you’re dealing with APIs that expectMaps, or you need to use any kind of key for grouping – not just keys that can be used as property names in JavaScri...
stationInfos = new Map<string, StationInfo>(); // 建立客户端连接 if (this.config.enableMqtt) { this.connectMqtt(); } // 加载缓存数据到内存中 this.LoadStations(); // 定时检查站点是否在线 // this.taskCheckStationOnline(); // 定时存储站点数据缓存 this.taskStoreStationData(); // 定时...
functionfoo(arg:unknown){if(typeofarg==="string"){// We know this is a string now.console.log(arg.toUpperCase());}} In this example, we checked whetherargwas astring. TypeScript recognized thetypeof arg === "string"check, which it considered a type guard, and was able to determine...
🗺️Road map Features that are planned: Promise support. Something likeassertOrReject<Type>(object)will eitherresolve(object)orreject(error). Optimize the generated conditions. Things likefalse || "key" === "key"can be simplified. Might be more interesting to publish a different library that...
interfaceCanCheck{checkThing:(x:string|number)=>boolean;}constobj={checkThing:(s:string)=>{returntrue;}}objsatisfiesCanCheck;// Alleged: should be OK This is wrong. Ifobjis aCanCheck, thenobj.checkThing(42)is legal, and42would appear ins, which is only allowed to be astring. ...
//Property 'name' has no initializer and is not definitely assigned in the constructor. } class GoodGreeter { name: string; constructor() { this.name = "hello"; } } 请注意,该字段需要在构造函数本身中进行初始化。 TypeScript 不会分析你从构造函数调用的方法来检测初始化,因为派生类可能会覆盖这...
reflect-metadata 存储元数据的方式是在对应的 target 对象上内建一个[[metadata]] 的属性,该属性对应的值是一个 WeakMap 数据类型的值,元数据内容就存在这个 Map 对象上,metadataKey 作为 WeakMap 的key, metadataValue 作为WeakMap对应的value值。 需要保证 metadataKey 、metadataValue 都需要是符合 ECMAScript ...