1.函数

1.1 重载

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function add(num1: number, num2: number): number; // 没函数体
function add(num1: string, num2: string): string;

function add(num1: any, num2: any): any {
  if (typeof num1 === 'string' && typeof num2 === 'string') {
    return num1.length + num2.length
  }
  return num1 + num2
}

const result = add(20, 30)
const result2 = add("abc", "cba")
console.log(result)
console.log(result2)

2.Type

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/**
 type A = {
  aa:string
  Bb:string
  cc_Dd:strng
 }

 type B = {
  aa:string
  bb:string
  ccDd:string
 }
 写一个camel类型完成这种转换
 */
type A = {
  aa: string
  Bb: string
  cc_Dd: string
  cc_dd_ee: boolean
}

type CamelCase<Str extends string> =
  Str extends `${infer left}_${infer rest}` ? 
  `${left}${rest extends `${infer left1}_${infer rest2}` ? CamelCase<Capitalize<string & rest>> : Capitalize<string & rest>}`
  : Lowercase<string & Str>

type camel<obj> = {
  [key in keyof obj as CamelCase<string & key>]: obj[key]
}

type res = camel<A>