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// 字符串数组中红黄蓝三种球排序
// 红蓝蓝黄红黄蓝红红黄红 => 黄黄黄红红红红红蓝蓝蓝

const fn = (arr) => {
    let yellow = [], red = [], blue = []
    arr.forEach(item => {
        switch (item) {
            case '黄':
                yellow.push(item)
                break
            case '红':
                red.push(item)
                break
            case '蓝':
                blue.push(item)
                break
        }
    })
    return yellow.concat(red, blue)
}

console.log(fn('红蓝蓝黄红黄蓝红红黄红'.split('')))