数组对象去重

    function perno(arr) {
        let map = new Map()
        for (const item of arr) {
          //查找perno重复的
          if (!map.has(item.perno)) {
            map.set(item.perno, item)
          }
        }
        return [...map.values()]
      }
      
      const arr = [
        { id: 1, name: '张三', perno: 12 },
        { id: 2, name: '黄颜', perno: 33 },
        { id: 3, name: '理想', perno: 33 },
        { id: 4, name: '小米', perno: 7 },
      ]
      
      const result = perno(arr)

 var arr = [
        { id: 1, city: '南京' },
        { id: 2, city: '南京' },
        { id: 3, city: '杭州' },
        { id: 4, city: '广州' },
      ]

      var newArr = arr.reduce((prev, cur) => {
        const existingItem = prev.find((item) => item.city === cur.city)
        if (!existingItem) {
          prev.push(cur)
        }
        return prev
      }, [])
      console.log(newArr)