1.剔除数组中id相同且name相同的对象元素,将保留前者。
let array=[
	{"id":"1","name":"a","age":"18"},
	{"id":"2","name":"b","age":"18"},
	{"id":"1","name":"c","age":"20"},
	{"id":"1","name":"a","age":"30"},
]

for (let i = 0; i < array.length; i++) {
	for (let j =i+1; j <array.length; ) {
    	if (array[i].id=== array[j].id&&
        	array[i].name=== array[j].name ) {//通过属性进行匹配；
            	array.splice(j, 1);//去除重复的对象；
        }else {
              j++;
        }
     }
}
console.log(array);
//  {"id":"1","name":"a","age":"18"},
//	{"id":"2","name":"b","age":"18"},
//	{"id":"1","name":"c","age":"20"},

2.计算数组中重复出现元素的个数
var arr = ["apple","orange","apple","orange","pear","orange"]; 
    function getWordCnt(){ 
        var obj = {}; 
        for(var i= 0, l = arr.length; i< l; i++){ 
            var item = arr[i]; 
            obj[item] = (obj[item] +1 ) || 1; 
        } 
        return obj; 
    }
    console.log(getWordCnt());//{apple: 2, orange: 3, pear: 1}

3.去除数组中changeBillNo相同的对象
let hash = {}; 
//去除changeBillNo相同的元素
array = array.reduce(function(item, next) { 
     hash[next.changeBillNo] ? '' : hash[next.changeBillNo] = true && item.push(next); 
     return item 
}, []) 

近期遇到一个项目，后台反的数据有重复，需要去重，去重的办法很多，这里用到了reduce去除数组中的重复数据，亲测可用

首先给大家看下我的数据格式
var list = [
    {"id":"1","score":"基础分"},
    {"id":"2","score":"社会贡献"},
    {"id":"2","score":"社会贡献"},
    {"id":"3","score":"工程质量"},
    {"id":"4","score":"信用评价"},
]

能看到id为2是重复的  需要去掉重复值，重新组成数组 直接上代码
    var hash = {};
    var newData = [...list]
    list = newData.reduce(function (item, next) {
     hash[next.value] ? '' : hash[next.value] = true && item.push(next);
        return item
      }, [])

输出list 得出结果
var list = [
    {"id":"1","score":"基础分"},
    {"id":"2","score":"社会贡献"},
    {"id":"3","score":"工程质量"},
    {"id":"4","score":"信用评价"},
]

 //去除数组中相同的对象
    deteleObject(obj) {
        var uniques = [];
        var stringify = {};
        for (var i = 0; i < obj.length; i++) {
            var keys = Object.keys(obj[i]);
            keys.sort(function (a, b) {
                return (Number(a) - Number(b));
            });
            var str = '';
            for (var j = 0; j < keys.length; j++) {
                str += JSON.stringify(keys[j]);
                str += JSON.stringify(obj[i][keys[j]]);
            }
            if (!stringify.hasOwnProperty(str)) {
                uniques.push(obj[i]);
                stringify[str] = true;
            }
        }
        uniques = uniques;
        return uniques;
    }

 

去除数组中重复的对象
const arr=[
	{
		id:1
		lable:'李白',
	},
	{
		id:1
		lable:'杜甫',
	},
	{
		id:2
		lable:'王维',
	}
]

const id='id' //这里定义按照过滤的对象的属性名称

const newArr = arr.reduce((all,next)=>all.some((item)=>item[id]==next[id])?all:[...all,next],[]);