使用for循环进行数组中对象去重和去null以及截取操作

//原数组
let objArr = [{
        specialName: ‘名称1‘
      },{
        specialName: ‘名称2‘
      },{
        specialName: ‘名称3‘
      },{
        specialName: ‘名称1‘
      },{
        specialName: null
      }]
let s = {}
let newObjArr = []
for (let i = 0;i < objArr.length; i++) {
console.log(objArr[i].specialName)
if ((!s[objArr[i].specialName] )&& objArr[i].specialName!=null) {
newObjArr.push(objArr[i]);
s[objArr[i].specialName] = true
}
}
console.log(newObjArr)
//输出结果：[{specialName: "名称1"},{specialName: "名称2"},{specialName: "名称3"}]

 let arr = [{ name: "测试", birthday: "2020-02-17", gender: 1, }, { name: "测试2", birthday: "2019-11-27", gender: 0, }]

    for (let i = 0; i < arr.length; i++) {
      console.log(arr[i])
      arr[i].birthday = arr[i].birthday.substring(0, 4) //截取birthday前四位
    }
    console.log(arr) //输出结果[{name: "测试", birthday: "2020", gender: 1},{name: "测试2", birthday: "2019", gender: 0}]