JS encapsulates the method of array inversion -- Feng Hao's blog

Ideas ： We use two loops Traverse the previous element and the next element respectively ,
Then define an empty variable , Make a position change

		function reversal(arr){
				for(var i =0 ;i<arr.length;i++){
					for(var j =i+1;j<arr.length;j++){
						var temp ;
						temp = arr[i];
						arr[i]=arr[j];
						arr[j]=temp;
					}
				}
			}
		
		var arr = ["a","b","c","d"];
		console.log(arr);
		reversal(arr);
		console.log(arr);