手撕代码——reduce函数

let Myreduce = function (func,init) {
  const list = [...this]
  let total
  if(init !== undefined) {
    total = init
  }else {
    total = list[0]
  }
  for(let i=0;i<list.length;i++) {
    total = func(tatal,list[i],i,this)
  }
}