R: Extend shinyjs by calling your own JavaScript functions
extendShinyjs
R Documentation
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 full README and demos
to learn more. Note that you have to install the 'V8' package in order to
use this function.
Usage
extendShinyjs(script, text, functions)
Arguments
script
Path to a JavaScript file that contains all the functions.
Each function name must begin with 'shinyjs.', for example
‘shinyjs.myfunc'. See ’Basic Usage' below.
text
Inline JavaScript code to use. If your JavaScript function is very
short and you don't want to create a separate file for it, you can provide the
code as a string. See 'Basic Usage' below.
functions
The names of the shinyjs JavaScript functions which you defined and
want to be able to call using shinyjs. Only use this argument if you cannot
install V8 on your machine. I repeat: do not use this argument if you're
able to install V8 on your machine. For example, if you defined JavaScript functions
named shinyjs.foo and shinyjs.bar, then use functions = c("foo", "bar").
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.
As the example above shows, after defining the JavaScript function
shinyjs.pageCol and passing it to extendShinyjs, it's possible
to call js$pageCol().
You can add more functions to the JavaScript code, but remember that every
function you want to use in R has to have a name beginning with
'shinyjs.'. See the section on passing arguments and the examples below
for more information on how to write effective functions.
Running JavaScript code on page load
If there is any JavaScript code that you want to run immediately when the page loads
rather than having to call it from the server, you can place it inside a
shinyjs.init function. The function shinyjs.init
will automatically be called when the Shiny app's HTML is initialized. A common
use for this is when registering event handlers or initializing JavaScript objects,
as these usually just need to run once when the page loads.
For example, the following example uses shinyjs.init to register an event
handler so that every keypress will print its corresponding key code:
Any shinyjs function that is called will pass a single array-like
parameter to its corresponding JavaScript function. If the function in R was
called with unnamed arguments, then it will pass an Array of the arguments;
if the R arguments are named then it will pass an Object with key-value pairs.
For example, calling js$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. This means that js$backgroundCol("blue", "test")
will not work because the arguments are unnamed and the JS function expects
the id to come before the colour. See the examples below for a shiny app
that uses this JS function.
Note
You still need to call useShinyjs() as usual, and the call to
useShinyjs() must come before the call to extendShinyjs().
The V8 package is strongly recommended if you use this function.
If you are deploying your app to shinyapps.io and are using extendShinyjs(),
then you need to let shinyapps.io know that the V8 package is required.
The easiest way to do this is by simply including library(V8) somewhere.
This is an issue with shinyapps.io that might be resolved by them in the future –
see here for more details.
See Also
runExample
Examples
## Not run:
Example 1:
Change the page background to a certain colour when a button is clicked.
jsCode <- "shinyjs.pageCol = function(params){$('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')
})
}
)
## End(Not run)