SOURCE

function flatArr(arr){
    let result=[]
    for(let i=0;i<arr.length;i++){
        if(Array.isArray(arr[i])){
            result = result.concat(flatArr(arr[i]))
        }else{
            result.push(arr[i])
        }
    }
    return result
}
const nestedArray = [1, [2, [3, 4], 5], 6];
const flattenedArray = flatArr(nestedArray);
console.log(flattenedArray); // 输出: [1, 2, 3, 4, 5, 6]