var array = ["page1","1973","Jimmy"]; 
var c;
for (i = 0; i < array.length; i++) {
if (array[i].indexOf("page") > -1){
c = i;}
} //returns 0 as the 1st entry is the one containing "page" (zero-based index)

I think this may help you. I had a similar issue. If your array looks like this:

var array = ["page1","1973","Jimmy"]; 

You can do a simple "for" loop to return the instance in the array when you get a match.

var c; 
for (i = 0; i < array.length; i++) {
if (array[i].indexOf("page") > -1){ 
c = i;}
} 

We create an empty variable, c to host our answer. We then loop through the array to find where the array object (e.g. "page1") matches our indexOf("page"). In this case, it's 0 (the first result)

Happy to expand if you need further support.