Discussion on: 10 JavaScript concepts you need to know for interviews

You are passing a reference, but you are not passing by reference.

If you were passing by reference, the variable inside the function would refer to the variable outside of the function.

See this PHP example.

<?php
$o = "foo";
function modifyVariable(&$n) {
  $n = "bar";
}
modifyVariable($o);
echo $o; // "bar"
?>

This is not the case in JavaScript - the variable inside the function is completely separate from the variable outside the function, but it refers to the same value.

You are given a reference to the value - you are not given the variable by reference.