SOURCE

let obj =  [[1,2,3],[1,[2,3,[4,5,6]]]]
//1、数组扁平化
//console.log(obj.flat(Infinity))
//2、正则
//let res =(obj+"").replace(/\[/g,'.').replace(/\]/g,'.').replace(/,/g,'.').split(".").map(v=>parseInt(v));
//3、递归
function myflat(arr){
    let res=[];
    for(let i = 0;i<arr.length;i++){
        // console.log(item,"item")
        if(Array.isArray(arr[i])){
            res = res.concat(myflat(arr[i]))
        }else{
            res = res.concat(arr[i])
        }
    }
    return res;
}

//排序
let sorted =myflat(obj);
sorted.sort((a,b) => b-a)

//去重
let nodup = [];
for(let item of sorted){
    if(!nodup.includes(item)){
        nodup.push(item)
    }
}

console.log(nodup)