Question

I will try and let the code speak for itself here: what if condition can I use to check if there will be another iteration after the current one?

$('#%id% td').each(function(){ 
if(??????????){                       // if there will be a next iteration
while($(this).height() == thisheight){
    // do something here on this iteration, but only if there will be another.
}  
}
});

Answer 1

Since it seems you want to process every element but the last one, you can simply remove the last element from the set, with .slice ^[docs]:

$('#%id% td').slice(0, -1).each(function() {
    // no need for `if` statement here
    // ...
});

The answer to your original question would be to compare the current iteration against the number of elements:

var $elements = $('#%id% td');
var max = $elements.length - 1;

$elements.each(function(index) { 
    if (index < max) {
        // ...
    }
    // ...
});