Answer 1

    var arr = '红蓝蓝黄红黄蓝红红黄红'
    var arrList = arr.split('')
    var obj = {
        "黄": [],
        "红": [],
        "蓝": []
    }
    arrList.map(item => obj[item].push(item))
    console.log([...obj['黄'], ...obj['红'], ...obj['蓝']].join(''))