对象数组，如果key中的value相同，不要该项

<script type="text/javascript">
  let arr=[
    {
      gradeId: "498094709437239572",
      gradeName: "2018级",
      stageId: "2",
      stageName: "初中",
    },
    {
      gradeId: "498094709437239572",
      gradeName: "2018级",
      stageId: "2",
      stageName: "初中1",
    },
    {
      gradeId: "498094709437239572",
      gradeName: "2018级",
      stageId: "2",
      stageName: "初中2",
    },
    {
      gradeId: "498094709437239572",
      gradeName: "2018级",
      stageId: "2",
      stageName: "初中1",
    },
    {
      gradeId: "498094709437239572",
      gradeName: "2018级",
      stageId: "2",
      stageName: "初中3",
    },
  ]
// 先找出不同的阶段，对象数组，如果key中的value相同，不要该项
let newArr=[]
let lastUseArr=[];
for(let i=0;i<arr.length;i++){
  if(newArr.indexOf(arr[i].stageName)==-1){
     newArr.push(arr[i].stageName)
     lastUseArr.push(arr[i])
  }
}  
console.log(lastUseArr)
</script>