R Programming By Example

How is functional reactivity handled within Shiny?

Reactivity is what makes your Shiny applications responsive. It seems like the application instantly updates itself whenever the user makes a change. However, in reality, Shiny is rerunning your R expressions in a carefully scheduled way every couple of microseconds, which creates the illusion of responsiveness. You don't need to know how reactivity occurs to use it, but understanding reactivity will make you a better Shiny programmer.

Remember that when we executed our very simple Shiny application in a previous section, the R console stopped being interactive? Well, that was happening because executing the shinyApp() function makes R busy by constantly monitoring and updating expressions ...