Not able to Remove previously inserted UI - r

Question

in the below app, I am not able to remove previously inserted UI. Not sure why. Could anyone please help...............................................................
---
title: "Untitled"
runtime: shiny
output:
flexdashboard::flex_dashboard:
orientation: columns
vertical_layout: fill
---
```{r setup, include=FALSE}
library(flexdashboard)
library(rhandsontable)
```r
Column {data-width=650}
-----------------------------------------------------------------------
### Insert and Remove UI
```{r}
actionButton("add", "Add UI")
actionButton("rmv", "Remove UI")
observeEvent(input$add, {
insertUI(
selector = "#add",
where = "afterEnd",
ui = textInput(paste0("txt", input$add),
"Insert some text"),multiple = FALSE
)
})
observeEvent(input$rmv, {
removeUI(
selector = "div:has(< #txt)"
)
})
```
```

Answer 1

We can get the previous ids using seq_len(input$add) where input$add is 1,2,3,... etc, then construct a jQuery statment using paste0 and sprintf
---
title: "Untitled"
runtime: shiny
output:
flexdashboard::flex_dashboard:
orientation: columns
vertical_layout: fill
---
```{r setup, include=FALSE}
library(flexdashboard)
library(rhandsontable)
```
Column {data-width=650}
-----------------------------------------------------------------------
```{r}
### Insert and Remove UI
actionButton("add", "Add UI")
actionButton("rmv", "Remove UI")
observeEvent(input$add, {
insertUI(
selector = "#add",
where = "afterEnd",
ui = textInput(paste0("txt", input$add),
sprintf("Insert some text for %i",input$add)),multiple = FALSE
)
})
observeEvent(input$rmv, {
removeUI(
#Remove the last UI
#selector = sprintf("div:has(> #txt%i)",input$add),
#Remove all previous UIs
selector = sprintf("div:has(%s)",paste0('> #txt', seq_len(input$add), collapse = ",")),
immediate = TRUE,
multiple = TRUE
)
})
```
Update
Remove the last UI every time user click Remove UI
### Insert and Remove UI
actionButton("add", "Add UI")
actionButton("rmv", "Remove UI")
data = reactiveValues(tmp=0)
observeEvent(input$add, {
data$tmp <- c(data$tmp,input$add)
insertUI(
selector = "#add",
where = "afterEnd",
ui = textInput(paste0("txt", input$add),
sprintf("Insert some text for %i",input$add)),multiple = FALSE
)
})
observeEvent(input$rmv, {
rm <- tail(data$tmp, 1)
data$tmp <- setdiff(data$tmp, rm)
removeUI(
#Remove the last UI
#selector = sprintf("div:has(> #txt%i)",input$add),
#Remove all previous UIs
selector = sprintf("div:has(%s)",paste0('> #txt', rm, collapse = ",")),
immediate = TRUE,
multiple = TRUE
)
})