js 獲取10個不重復隨機數

	var arr1 = new Array();
			var arr2 = new Array();
			for(var i = 0; i<20; i++){
				
				arr1.push(i);
				
			}
			
			
			
			
			for(var k = 0; k<10;k++){
				
				var id = Math.ceil(Math.random()*19);	 			
				if(arr2.indexOf(arr1[id]) === -1){
					arr2.push(arr1[id]);					
				}else{					
					k= k - 1;
					continue;
				}			  
			}
			
			console.log(arr2);