js配列オブジェクトのデフラグ

var arr = [{
   key: '01',
   value: '  '
  }, {
   key: '02',
   value: '  '
  }, {
   key: '03',
   value: '  '
  },{
   key: '04',
   value: '  '
  },{
   key: '01',
   value: '  '
  }];
  //   1：           ，         key
  var result = [];
  var obj = {};
  for(var i =0; i){
   if(!obj[arr[i].key]){
     result.push(arr[i]);
     obj[arr[i].key] = true;
   }
  }
 
const result = []
const obj = {}
for (let i = 0; i < data.length; i++) {
    if (!obj[data[i].key]) {
        result.push(data[i])
        obj[data[i].key] = true
    }
}
console.log('result ', result)
  console.log(result); // [{key: "01", value: "  "},{key: "02", value: "  "},{key: "03", value: "  "},{key: "04", value: "  "}]
  //   2：  reduce      ,reduce               ，      item    
  var obj = {};
  arr = arr.reduce(function(item, next) {
   obj[next.key] ? '' : obj[next.key] = true && item.push(next);
   return item;
  }, []);
  console.log(arr); // [{key: "01", value: "  "},{key: "02", value: "  "},{key: "03", value: "  "},{key: "04", value: "  "}]