dynamic - How to add/remove input fields dynamically by a button in shiny -

i've been trying find solution how add , remove input fields button in shiny. don't have source code since haven't made progress, jquery example (http://www.mkyong.com/jquery/how-to-add-remove-textbox-dynamically-with-jquery/) gives idea on i'm trying accomplish. possible in shiny or should use shinyjs this? thank in advance!

edit: read jquery example bit more, , added code snippet doing think looking for.

i don't know jquery, couldn't make out of example link. took guess on wanted, think key idea use of renderui , uioutput if suggestion here misses point.

to toggle ui element:

if don't want use shinyjs, this:

library(shiny)  ui <- shinyui(fluidpage(    actionbutton("btn", "toggle textbox"),    textoutput("btn_val"),   uioutput("textbox_ui")  ))  server <- shinyserver(function(input, output, session) {    output$btn_val <- renderprint(print(input$btn))    textboxtoggle <- reactive({      if (input$btn %% 2 == 1) {       textinput("textin", "write something:", value = "hello world!")     }    })    output$textbox_ui <- renderui({ textboxtoggle() })  })  shinyapp(ui, server) 

add , remove elements:

after reading bit of jquery example, think similar looking for:

library(shiny)  ui <- shinyui(fluidpage(    sidebarpanel(        actionbutton("add_btn", "add textbox"),       actionbutton("rm_btn", "remove textbox"),       textoutput("counter")      ),    mainpanel(uioutput("textbox_ui"))  ))  server <- shinyserver(function(input, output, session) {    # track number of input boxes render   counter <- reactivevalues(n = 0)    observeevent(input$add_btn, {counter$n <- counter$n + 1})   observeevent(input$rm_btn, {     if (counter$n > 0) counter$n <- counter$n - 1   })    output$counter <- renderprint(print(counter$n))    textboxes <- reactive({      n <- counter$n      if (n > 0) {       lapply(seq_len(n), function(i) {         textinput(inputid = paste0("textin", i),                   label = paste0("textbox", i), value = "hello world!")       })     }    })    output$textbox_ui <- renderui({ textboxes() })  })  shinyapp(ui, server) 

the problem approach each time press add or remove button, of input boxes re-rendered. means input might have had on them disappears.

i think around saving current input values of input boxes reactivevalues object, , setting values object starting values of re-rendered input boxes using value option in textinput. i'll leave implementation of now, though.