Why does "use strict" not respect variable scope

Question

I have a question regarding the usage of "use strict" variables.

Why does the following fail silently instead of throwing an error?

"use strict"; 
var $class = {};
$class.rowsICanDisplay = 10;
$class.difference = -1;
var absDifference = 1;
var gridTableBody = $('#mytable tbody');
//code removed for clarity
if($class.difference > 0) {
    var offset = $class.rowsICanDisplay - absDifference; // mistake should be declared in outer scope
    //code removed for clarity
    $('tr:lt(' + offset + ')', gridTableBody).remove();
}
else {
     //code removed for clarity
     $('tr:gt(' + offset + ')', gridTableBody).remove(); // why does this fail silently
}

Answer 1

Because Javascript doesn't have block scope.
Any variable declared anywhere in a function is visible to the entire function.

JSHint will catch this problem.

Answer 2

$('tr:gt(' + offset + ')', gridTableBody).remove(); // why does this fail silently

Because offset is not defined in the context of your else block, so your selector is invalid and isn't matching anything.

Answer 3

In the else statement, offset is not defined. You need to pull it out and define it outside of the "if" structure.