删除数组undefind的值
var arr = [1, 2, undefined, 3, 4];
for(var i = 0; i < arr.length; i++){
if(arr[i] == '' || arr[i] == null || typeof(arr[i]) == undefined) {
arr.splice(i,1);
i=i-1;
}
}
console.log(arr)
//结果
![](https://img2020.cnblogs.com/blog/1303454/202009/1303454-20200927091543616-1550326667.png)