ios-calculator | An iOS Calculator clone using HTML , CSS , and JavaScript | Apps library

The difference between a switchnavigator and a stacknavigator is whether you stack the stack or not. StackNavigator builds up the stack by default each time you move the screen. This means that you'll see the screen on top of the screen You can therefore execute the 'goBack()' button. However, the switchnavigator does not stack. The switchnavigator resets the path as it moves the screen.

SwitchNavigator: The purpose of SwitchNavigator is to only ever show one screen at a time. By default, it does not handle back actions and it resets routes to their default state when you switch away

StackNavigator: Provides a way for your app to transition between screens where each new screen is placed on top of a stack.

The reason this is occurring is because you're checking the className attribute, which contains all classes of the element. The first time it's being checked, the value is not horizontal-nav -- it's horizontal-nav desktop-site, which causes the code in the else block to fire. The second time around, it is horizontal-nav, so it works correctly.

Use x.classList.contains("horizontal-nav"), or build/use a method to check whether className contains horizontal-nav rather than is horizontal-nav. jQuery's hasClass works perfectly for this, if you need to support older browsers.