返回数组的层深

let deep=1;

function array_depths(arr){

let maxDeep=1;

arr.forEach(item=>{

if( typeof item == 'object'){

deep = array_depths(item) + 1;

maxDeep=deep>maxDeep?deep:maxDeep;

}

})

return maxDeep;

}

console.log(array_depths([1,2,[3,4],[6,[7,[8,[9]]]]])) //5