3.6 Reactive expressions

What - A tool that reduces duplication in your reactive code by introducing additional nodes into the reactive graph

How - using reactive()

# Just for example

server <- function(input, output, session) {
  string <- reactive(paste0("Hello ", input$name, "!"))
  output$greeting <- renderText(string())
}

In other words, reactive makes apps cleaner & more efficient (by removing redundant codes & recomputation). It also simplifies the reactive graph.

Reactive expressions have a flavour of both inputs and outputs:

• Like inputs, you can use the results of a reactive expression in an output.
• Like outputs, reactive expressions depend on inputs and automatically know when they need updating.