• 交叉類型&：交集

type A = string & number // never

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• interface使用extends的話，發現有類型沖突會直接沖突，因此在定義可擴展的類型時最好用interface
• 函數的交集會得到參數的并集

type A = {
  method: (n:string) => void
}

type B = {
  method: (n:number) => void
} & A

const x:B = {
  // n:string | number
  method:(n)=>{
   console.log(n);
  }
}

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type Fn1 = (n:string) => void
type Fn2 = (n:number) => void
type Fn = Fn1 & Fn2
// n: string | number
const fn: Fn = (n)=> console.log();

• 具體理解 |，ts聲明時檢查緊，賦值時檢查松

type A = {
  name: string
}

type B = {
  age: number
}

type C = A | B

// 都正確
const p:C = {name:'x'}
const p:C = {age: 12}

// error，不能有gender屬性
const x:C = {
  name:'',
  age: 12,
  gender: ''
}
------------------------------------
// 不報錯
const d = {
  name: '',
  age: 12,
  gender: '' 
}
const p:C = d