JS數組扁平化(flat)

function flatten(arr){
        var newArr=[]
        for(var i=0;i<arr.length;i++){
            if(Array.isArray(arr[i])){
                newArr=newArr.concat(flatten(arr[i]))
            }else{
                newArr.push(arr[i])
            }
        }
        return newArr
    }
    console.log(flatten([1,2,[5,6,[7,8,[4,5]],10]]))