SOURCE

//根据confid取配置差异项
function uniqueConfid(arr, num) {
    //计数
    const counts = arr.reduce(
        (m, x) => ((m[x.confid] = (m[x.confid] || 0) + 1), m), {}
    );
    //去重
    const res = new Map();
    const newArr = arr.filter(item => {
        return !res.has(item.confid) && res.set(item.confid, 1);
    });
    //删除最多重复项
    return newArr.filter(x => counts[x.confid] !== num);
}
let arr = [{
    confid: 1
}, {
    confid: 1
}, {
    confid: 2
}, {
    confid: 3
}, {
    confid: 4
}];
console.log('输出结果：', JSON.stringify(uniqueConfid(arr, 2)))