Mastering TypeScript 3 - Third Edition

Concrete states

Now, let's examine the three concrete state classes, as follows:

export class MainPanelOnly  
    implements IState { 
    getPanelType() : PanelType { return PanelType.Primary; } 
    getStateType() : StateType { return StateType.MainPanelOnly; } 
    getPanelButtonClass() : string { return 'fa-chevron-right';} 
    isSideNavVisible() : boolean { return false; } 
} 

We start with a state class named MainPanelOnly, which is used to describe the state when the side navigation bar is not visible, and we are on the main viewing panel. This is a very simple class that implements the IState interface and as such, simply returns the correct values for each of the four functions. As we can see by the return values, we are on PanelType.Primary, the isSideNavVisible ...