const x = "hello" as number;// Conversion of type 'string' to type 'number' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.有的时候，这条规则会显得非常保守，阻止了你原本有效的类型转换。如果发生...
ts复制代码/** * Convert string literal type to uppercase */ type Uppercase<S extends string> = intrinsic; 21. Lowercase<StringType> 作用: 将字符串中的每个字符转换为对应的小写。 常用指数: ⭐️⭐️⭐️⭐️ 使用场景示例: ts复制代码type Greeting = 'Hello, world' type QuietGre...
typescript复制代码function reverse(x: number): number; function reverse(x: string): string; function reverse(x: number | string): number | string { if (typeof x === 'number') { return Number(x.toString().split('').reverse().join('')); } else if (typeof x === 'string') { ...
type FirstType= Types[0];//stringtype LastType = Types[2];//booleantype Length = Types['length']//3 还能拿 length 哦type AllTypes = Types[number];//string | number | boolean 这也是把 Tuple 转换成 Union 的方法 最后一句也是 convert Tuple to Union 的方式哦. Indexed Access Types + key...
first set the type of the string tounknown. This is because, by default, TypeScript considers any conversion of typestringto anumberto be potentially a mistake. This is because neither string nor number sufficiently overlaps with the other. To convert a string to a number using as proceed as...
function computeTypes(one: string, two: number) { const nums = [two];const strs = [one]return { nums,strs } // 返回 { nums: number[]; strs: string[] } 的类型 } 请记住：这是一个很重要也很有意思的特性，函数返回值的类型推断结合泛型可以实现特别复杂的类型计算（本质是复杂的类型推断...
function operator(x: unknown) { if(isString(x)) { // ok x 类型缩小为 string } if (isNumber(x)) { // ts(2345) unknown 不能赋值给 number } } 在上述代码中,在添加返回值类型的地方,我们通过“参数名 + is + 类型”的格式明确表明了参数的类型,进而引起类型缩小,所以类型谓词函数的一个重要...
例如: typescript复制代码function convertToString<T>(value: T): string { return value as unknown as string; } 在上述示例中,通过连续使用类型断言,我们将泛型类型 T 先断言为 unknown 类型,然后再断言为字符串类型,将参数 value 转换为字符串类型并返回。
比如如果我们将上边示例中的 convertToUpperCase 函数使用 TypeScript 实现，那么就需要显示地标明 strOrArray 的类型就是 string 和 string[] 类型组成的联合类型，如下代码所示：{ const convertToUpperCase = (strOrArray: string | string[]) => { if (typeof strOrArray === 'string') { return strOr...
functionrefEventEmitter(event?:string):void;functionrefEventEmitter(event:string,callback:()=>void):void;functionrefEventEmitter(callback:()=>void):void;functionrefEventEmitter(...args:|[event?:string]|[event:string,callback:()=>unknown,]|[callback:()=>unknown]):void{let[event,callback]=args...