It should be because IE8 does not support indexOf, so write a for loop method to determine whether it exists and return true false
function isCon(arr, val){
for(var i=0; i<arr.length; i++){
if(arr[i] == val)
return true;
}
return false;
}Add this method in js and call the method at the calling location
window.onload = function(){
var arr=new Array(1,2,3,2,4,2,5,6,7,2,4,3,18,12,41,87);
alert(isCon(arr, 8));
}
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
