function isNumber(x: any): x is number { return typeof x === "number"; } function isString(x: any): x is string { return typeof x === "string"; } function padLeft(value: string, padding: string | number) { if (isNumber(padding)) { return Array(padding + 1).join(" ") +...
boolean:(input:boolean)=>(input?"true":"false"),};constformat=(input:string|number|boolean)=>{constinputType=typeofinputas"string"|"number"|"boolean";constformatter=objOfFunctions[inputType];returnformatter(input);// Error: Argument of type 'string | number | boolean'...
1functionschools(type:number):number;2functionschools(type:string):string;3functionschools(type:number | string |boolean):number | string |boolean{4if(typeoftype === "number"){5returntype.toFixed(2);6}elseif(typeoftype === "string"){7returntype.substring(0,1);8}elseif(typeoftype ==...
在TypeScript中获取泛型类型参数可以通过使用typeof和keyof关键字结合泛型参数来实现。下面是一个示例: 代码语言:txt 复制 function getType<T>(arg: T): T { return arg; } type MyType = typeof getType; // 获取函数的类型 type MyArgumentType = Parameters<MyType>[0]; // 获取函数参数的类型 c...
functiongreet(name:string):string{return`Hello,${name}!`;}console.log(greet("Alice"));// 输出: Hello, Alice! 1. 2. 3. 4. 在上述示例中,greet函数接受一个名为name的参数,并指明该参数是一个string类型。返回值也是string类型。 二、可选参数和默认参数 ...
functionfirstElement<Type>(arr:Type[]):Type|undefined{returnarr[0];} 通过给函数添加一个类型参数Type,并且在两个地方使用它,我们就在函数的输入(即数组)和函数的输出(即返回值)之间创建了一个关联。现在当我们调用它,一个更具体的类型就会被判断出来: ...
functioncompare(a:string,b:string):-1|0|1{returna===b?0:a>b?1:-1;} 当然了,你也可以跟非字面量类型联合: interfaceOptions{width:number;}functionconfigure(x:Options|"auto"){// ...}configure({width:100});configure("auto");configure("automatic");// Argument of type '"automatic"' is...
function getProperty<Type, Key extends keyof Type>(obj: Type, key: Key) { return obj[key]; } let x = { a: 1, b: 2, c: 3, d: 4 }; getProperty(x, "a"); getProperty(x, "m"); //Argument of type '"m"' is not assignable to parameter of type '"a" | "b" | "c" |...
typeParam = ParamType<FunctionType>;// type Param = number typeOtherParam = ParamType<symbol>;// type Param = symbol 判断T 是否能赋值给 (param: infer P) => any,并且将参数推断为泛型 P,如果可以赋值,则返回参数类型 P,否则返回传入的类型 ...
functiongreet(name:string){console.log("Hello "+name.toUpperCase());}//Argument of type 'number' is not assignable to parameter of type 'string'greet(123);greet("abc","cba");//Expected 1 arguments, but got 2.ts(2554) 2. 函数的返回值类型 ...