Promise

// promise对象 指定类型 特殊   :Promise<resolve返回的类型>
interface ResItf{
  code:number;
  data:{a:number,b:number}[];
  message:string;
}

let p:Promise<ResItf> = new Promise((resolve,reject)=>{
    resolve({
      code:0,
      data:[{a:1,b:2},{a:11,b:22}],
      message:""
    })
})

p.then(res=>{
  if(res.code==0){
    res.data.map(item=>item.a)
  }
})