可以缓存promise结果的辅助函数

memoizePromise.js

export var memoizePromise = function(fun){
  var cache = {};
  return function(...args){
    var key = args.toString();
    return new Promise(function(resolve, reject){
      if(cache[key]){
        return resolve(cache[key])
      }else{
        fun.apply(this, args).then((data)=>{
          cache[key] = data;
          resolve(data)
        }, (err)=>{
          reject(err)
        })
      }
    })
  }
}