Pass reactive meta tag to browser?

Tuija Sonkkila

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Apr 11, 2017, 3:39:10 AM4/11/17

to Shiny - Web Framework for R

I'm trying to get the Unpaywall browser extension to read a meta tag from within the app. The tag is added to DOM when the user filters one row from a DT table.

Is there a way to pass this reactive meta tag info to the browser?

Some demo data articles.csv:

"Article","DOI"
"First","doi:10.1039/C4CP02345G"
"Second","doi:10.1039/C4CP02175G"
"Third","doi:10.1039/C4CP02325G"
...

global.R:

library(shiny)

data <- read.table("articles.csv", header = T, sep = ",", stringsAsFactors = F)

server.R:

library(DT)

shinyServer(function(input, output, session) {
  
  output$x1 = DT::renderDataTable(data, server = FALSE)
  
  output$addtag <- renderUI({  
    
    # From example https://yihui.shinyapps.io/DT-info/
    t1 = input$x1_rows_current
    
    tt <- if (is.null(t1) || t1 == '') 'Nothing' else {
      data[t1, "DOI"]
    }
    
    tags$meta(name="doi", content=tt)
    
  })
  
})

ui.R:

fluidPage(
  title = 'DataTable on articles',
  
  uiOutput("addtag"),
  
  h1('Table'),
  fluidRow(
    column(6, DT::dataTableOutput('x1')),
    column(6, plotOutput('x2', height = 500))
  )
)

Bárbara Borges

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Apr 20, 2017, 10:33:25 PM4/20/17

to Shiny - Web Framework for R

I think what you're looking for for this case is insertUI. Try this and let me know if it does what you want:

library(shiny)

data <- read.table("articles.csv", header = T, sep = ",", stringsAsFactors = F)

ui <- fluidPage(

title = 'DataTable on articles',

  h1('Table'),
  fluidRow(
    column(6, DT::dataTableOutput('x1')),
    column(6, plotOutput('x2', height = 500))
  )
)

server <- function(input, output, session) {
  
  output$x1 <- DT::renderDataTable(data, server = FALSE)
  
  observe({
    t1 <- input$x1_rows_current

    tt <- if (is.null(t1) || t1 == '') 'Nothing' else {
      data[t1, "DOI"]
    }

    insertUI(
      selector = "head", where = "beforeEnd", immediate = TRUE,
      tags$head(tags$meta(name="doi", content=tt))
    )
  })
}
shinyApp(ui, server)

Tuija Sonkkila

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Apr 22, 2017, 5:37:47 AM4/22/17

to Shiny - Web Framework for R

Thank you Bárbara, this was a clear step forward. Preceded with a removeUI, the observe function below now first deletes all previous meta elements, and then adds a new one based on the selection. However, all of this still seem to be too late as far as the browser extension is concerned; it does not fire up. Anyway, at least I believe I am now on the right track. I suppose that next I'd need some advice from the makers of the extension. Thanks again, learned something new about Shiny!

 observe({
    t1 <- input$x1_rows_current
    tt <- if (is.null(t1) || t1 == '') NULL else {
      data[t1, "DOI"]
    }
    removeUI(
      selector = "[name='doi']", 
      multiple = TRUE,
      immediate = TRUE
    )

    insertUI(
      selector = "head", where = "beforeEnd", immediate = TRUE,
      tags$head(tags$meta(name="doi", content=tt))
    )
  })

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