【JS】数组扁平化

[Easay]

reduce方法

function flatten1(arr){
    return arr.reduce((pre,cur)=>{
        Array.isArray(cur)?pre = pre.concat(flatten1(cur)):pre.push(cur);
        return pre;
    },[]);
}

循环

function flatten2(arr){
    let res = [];
    for(let i=0;i<arr.length;i++){
        if(Array.isArray(arr[i])){
            res = res.concat(flatten2(arr[i]));
        }else{
            res.push(arr[i]);
        }
    }
    return res;
}

在原数组上修改

// 原数组上修改
function flatten3(arr){
    for(let i=0;i<arr.length;i++){
        if(Array.isArray(arr[i])){
            flatten3(arr[i]);
            let len = arr[i].length;
            arr.splice(i,1,...arr[i]);
            i = i+len-1;
        }
    }
}
let c = [1,[2,3,[4,5,6]]];
flatten3(c);
console.log(c);

[Easay]

数据扁平化并排序

function flatten(arr){
    const dfs = function(arr){
        return arr.reduce((pre,cur)=>{
            Array.isArray(cur)?pre=pre.concat(dfs(cur)):pre.push(cur)
            return pre
        },[])
    }
    const resultArr = dfs(arr)
    resultArr.sort((a,b)=>a-b)
    return resultArr
}
const arr = [[1,2,3],[4,5],9,8,7]
console.log(flatten(arr))