运行以后为什么有一个undefined呢？求大神告知

function arr(){
	           	var arr1 = ['1', '4', '66', '99', '12', '3', '10'];
	           	var arr2 = [];
	           	for(var i = 0; i < arr1.length; i++){
	           		if(arr1[i] != 10){
	           			arr2[arr2.length] = arr1[i]
	           		}
	           	}
           		console.log(arr2)
           }

我这边没问题啊，

"1,4,66,99,12,3"