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...
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...
function Log(target: Function, key: string, parameterIndex: number) { let functionLogged = key || target.prototype.constructor.name; console.log(`The parameter in position ${parameterIndex} at ${functionLogged} has been decorated`); } class Greeter { greeting: string; constructor(@Log phrase:...
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...
letsym1=Symbol();letsym2=Symbol('key');// 可选的字符串keyletsym3=Symbol('key');sym2===sym3;//false 对象类型 object、Object 以及 { } object 看图可以发现,当赋值给object的类型为number、string、boolean时都会报错,而null和undefined因为我关闭了严格模式所以不会报错。
function(target: any, propertyKey: string, descriptor: PropertyDescriptor) { // Save a reference to the original methodvar originalMethod = descriptor.value; descriptor.value = function (...args: any[]) { var argsLog = args.map(a => ...
TypeScript has a way to declare new names for types called type aliases. If you’re writing a set of functions that all work onstring | number | boolean, you can write a type alias to avoid repeating yourself over and over again. ...
Exception: new Map<string, number>() is OK. Using the types Function and Object is almost never a good idea. In 99% of cases it's possible to specify a more specific type. Examples are (x: number) => number for functions and { x: number, y: number } for objects. If there is...
Hash map{ [key :string] :Type; } Indexable types{ [id :number] :Type; } Arrays ConceptCode Array of stringsstring[]orArray<string> Array of functions that return boolean{() :boolean;}[]orArray<()=>boolean> Indexable Interface
Please don't hesitate to ask questions if/when you run into issues with the environment! Naoki-Hada wrote I was using WebStorm for IDE. I'll check with VS Code as well. WebStorm has support for TypeScript so you could probably get it working there! One of the benefits of VSCode is ...