math within an document.getElementById tag?

caution: newbie javascript question

let update[2] = 10 just for arguments sake

Code:

document.getElementById("next").innerHTML = "<a href=\"javascript:sndReq('nextImage|" + update[2]+1 + "')\">Next Image</a><br>";

im learning ajax, but having never known javascript, but i did take a course on java in college

my question is, the variable update[2]+1 should print out 11 if update[2] is 10, but instead, it comes up with 101, it just adds the one onto the end of 10, so i thought maybe its a string? so i tried to parseInt it, and still no go, help plz?

 

eval(parseInt(update[2])+1)

 

thanks