Array数组展平

多维数组数据展平：let arr = [1,[3,2,[4]]]

let arr = [1,[3,2,[4]]]
let flatten = (arr)=>{
	// '1,3,2,4' => ['1','3','2','4'] => [1,3,2,4]
	return (arr + '').split(',').map(str=>parseInt(str))
}

let flatten = (arr)=>{
	let retArr = []
    arr.forEach(item=>{
    	if(Array.isArray(item)){
        	retArr.push(...flatten(item))
        }else{
        	retArr.push(item)
        }
    })
    return retArr
}


// 去重升序
let sortArr = (arr)=>{
	return [...new Set(arr.sort((a,b)=>a-b))]
}

console.log(flatten(arr), sortArr(flatten(arr)))