shinyjs (version 1.0)

extendShinyjs: Extend shinyjs by calling your own JavaScript functions

Description

Add your own JavaScript functions that can be called from R as if they were regular R functions. This is a more advanced technique and can only be used if you know JavaScript. See 'Basic Usage' below for more information or view the shinyjs webpage to learn more.

Usage

extendShinyjs(script, text, functions)

Value

Scripts that shinyjs requires in order to run your JavaScript functions as if they were R code.

Basic Usage

Any JavaScript function defined in your script that begins with `shinyjs.` will be available to run from R through the `js$` variable. For example, if you write a JavaScript function called `shinyjs.myfunc`, then you can call it in R with `js$myfunc()`.

It's recommended to write JavaScript code in a separate file and provide the filename as the script argument, but it's also possible to use the text argument to provide a string containing valid JavaScript code. Using the text argument is meant to be used when your JavaScript code is very short and simple.

As a simple example, here is a basic example of using extendShinyjs to define a function that changes the colour of the page.

library(shiny)
library(shinyjs)
jsCode <- "shinyjs.pageCol = function(params){$('body').css('background', params);}"
shinyApp(
  ui = fluidPage(
    useShinyjs(),
    extendShinyjs(text = jsCode),
    selectInput("col", "Colour:",
                c("white", "yellow", "red", "blue", "purple"))
  ),
  server = function(input, output) {
    observeEvent(input$col, {
      js$pageCol(input$col)
    })
  }
)

As the example above shows, after defining the JavaScript function shinyjs.pageCol and passing it to extendShinyjs, it's possible to call js$pageCol().

You can add more functions to the JavaScript code, but remember that every function you want to use in R has to have a name beginning with `shinyjs.`. See the section on passing arguments and the examples below for more information on how to write effective functions.

Running JavaScript code on page load

If there is any JavaScript code that you want to run immediately when the page loads rather than having to call it from the server, you can place it inside a shinyjs.init function. The function shinyjs.init will automatically be called when the Shiny app's HTML is initialized. A common use for this is when registering event handlers or initializing JavaScript objects, as these usually just need to run once when the page loads.

For example, the following example uses shinyjs.init to register an event handler so that every keypress will print its corresponding key code:

jscode <- "
shinyjs.init = function() {
  $(document).keypress(function(e) { alert('Key pressed: ' + e.which); });
}"
shinyApp(
  ui = fluidPage(
    useShinyjs(),
    extendShinyjs(text = jscode),
    "Press any key"
  ),
  server = function(input, output) {}
)

Passing arguments from R to JavaScript

Any shinyjs function that is called will pass a single array-like parameter to its corresponding JavaScript function. If the function in R was called with unnamed arguments, then it will pass an Array of the arguments; if the R arguments are named then it will pass an Object with key-value pairs.

For example, calling js$foo("bar", 5) in R will call shinyjs.foo(["bar", 5]) in JS, while calling js$foo(num = 5, id = "bar") in R will call shinyjs.foo({num : 5, id : "bar"}) in JS. This means that the shinyjs.foo function needs to be able to deal with both types of parameters.

To assist in normalizing the parameters, shinyjs provides a shinyjs.getParams() function which serves two purposes. First of all, it ensures that all arguments are named (even if the R function was called without names). Secondly, it allows you to define default values for arguments.

Here is an example of a JS function that changes the background colour of an element and uses shinyjs.getParams().

shinyjs.backgroundCol = function(params) {
  var defaultParams = {
    id : null,
    col : "red"
  };
  params = shinyjs.getParams(params, defaultParams);
var el = $("#" + params.id);
  el.css("background-color", params.col);
}

Note the defaultParams object that was defined and the call to shinyjs.getParams. It ensures that calling js$backgroundCol("test", "blue") and js$backgroundCol(id = "test", col = "blue") and js$backgroundCol(col = "blue", id = "test") are all equivalent, and that if the colour parameter is not provided then "red" will be the default.

All the functions provided in shinyjs make use of shinyjs.getParams, and it is highly recommended to always use it in your functions as well. Notice that the order of the arguments in defaultParams in the JavaScript function matches the order of the arguments when calling the function in R with unnamed arguments.

See the examples below for a shiny app that uses this JS function.

See Also

runExample

Examples

# NOT RUN {
  Example 1:
  Change the page background to a certain colour when a button is clicked.

    jsCode <- "shinyjs.pageCol = function(params){$('body').css('background', params);}"

    shinyApp(
      ui = fluidPage(
        useShinyjs(),
        extendShinyjs(text = jsCode),
        selectInput("col", "Colour:",
                    c("white", "yellow", "red", "blue", "purple"))
      ),
      server = function(input, output) {
        observeEvent(input$col, {
          js$pageCol(input$col)
        })
      }
    )

    # If you do not have `V8` package installed, you will need to add another
    # argument to the `extendShinyjs()` function:
    # extendShinyjs(text = jsCode, functions = c("pageCol"))

  ==============

  Example 2:
  Change the background colour of an element, using "red" as default

    jsCode <- '
    shinyjs.backgroundCol = function(params) {
      var defaultParams = {
        id : null,
        col : "red"
      };
      params = shinyjs.getParams(params, defaultParams);

      var el = $("#" + params.id);
      el.css("background-color", params.col);
    }'

    shinyApp(
      ui = fluidPage(
        useShinyjs(),
        extendShinyjs(text = jsCode),
        p(id = "name", "My name is Dean"),
        p(id = "sport", "I like soccer"),
        selectInput("col", "Colour:",
                    c("white", "yellow", "red", "blue", "purple")),
        textInput("selector", "Element", "sport"),
        actionButton("btn", "Go")
      ),
      server = function(input, output) {
        observeEvent(input$btn, {
          js$backgroundCol(input$selector, input$col)
        })
      }
    )

  ==============

  Example 3:
  Create an `increment` function that increments the number inside an HTML
  tag (increment by 1 by default, with an optional parameter). Use a separate
  file instead of providing the JS code in a string.

  Create a JavaScript file "myfuncs.js":
    shinyjs.increment = function(params) {
      var defaultParams = {
        id : null,
        num : 1
      };
      params = shinyjs.getParams(params, defaultParams);

      var el = $("#" + params.id);
      el.text(parseInt(el.text()) + params.num);
    }

  And a shiny app that uses the custom function we just defined. Note how
  the arguments can be either passed as named or unnamed, and how default
  values are set if no value is given to a parameter.

      library(shiny)
      shinyApp(
        ui = fluidPage(
          useShinyjs(),
          extendShinyjs("myfuncs.js"),
          p(id = "number", 0),
          actionButton("add", "js$increment('number')"),
          actionButton("add5", "js$increment('number', 5)"),
          actionButton("add10", "js$increment(num = 10, id = 'number')")
        ),
        server = function(input, output) {
          observeEvent(input$add, {
            js$increment('number')
          })
          observeEvent(input$add5, {
            js$increment('number', 5)
          })
          observeEvent(input$add10, {
            js$increment(num = 10, id = 'number')
          })
        }
      )
# }