check valid tag id

[reubin haz]

I'd like to check if a given tag ID exists or not. I tried
typeof document.getElementById(givenID).innerHTML != "string"
or
document.getElementById(givenID).innerHTML != null

but both of them fail. Does someone know how to check if the given tag id is valid?

thanks.

[Eric Pascarello]

if(typeof(document.getElementById("someId")) != "undefined")alert("I am here");