JS written test question -- realize the flat function of array

		Array.prototype.myflat=function(count){
             let arr=[];
             // Traversing the members of an array 
			 for(let i=0;i<this.length;i++){
			 // Determine whether members are arrays 
				 if(this[i].constructor==Array&&count>0){   // When the dimension is <=0 Then stop 
				 // If it is an array, use the idea of function self calling , Cycle again 
					let arr1=this[i].myflat(count-1)  // here count It represents the descending dimension 
					// Ergodic out arr1 Members of , Put in what we return arr in   Because we call the function to return an array, we have to traverse 
					arr.push(...arr1)
				 }else{arr.push(this[i])}
			 }
			 return arr;
		}
		var arr=[[1,2,3],8,9,[[1,2],[2,3]],[[[1,2]]]]
        console.log(arr.myflat(3))