Javascript Namespacing And This/that Scope

I am working on namespacing some applications and I am not understanding scope within a namespace. (function (App) { App.Test = function(props){ var that = this;

Solution 1:

JavaScript is pass/call/assign by value. That means that a variable or property will always contain a value, but never a reference to a variable. I.e. assigning a new value to a variable or property does not change the value of another variable or property (exceptions are global scope and with scopes, where the variable bindings are connected to an object).

Example:

var foo = 42;
var bar = foo;
foo = 21;
console.log(bar); // 42

bardoes not have a reference to foo. Instead the value of foo is copied to bar. Thus changing foo or bar later on does not impact the other variable.

Compare that to PHP where we can actually assign a variable by reference using a special operator:

$foo = 42;
$bar = &$foo;
$foo = 21;
echo$bar; // 21

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Applied to your example:

When you do that.letter = letter, you are copying the value of letter to that.latter. Now both bindings have the same value.

Later when you assign letter = "B"; and that.letter = "C";, you are assigning new values to the variable and the property and now they have different values.

I might be missing something from your question, but I don't see how the issue has anything to do with this or namespaces in particular.