Custom JavaScript, CSS and HTML in Shiny

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Deepanshu Bhalla
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In this tutorial, I will cover how to include custom JavaScript, CSS and HTML code in your R shiny app. By including them, you can make a very powerful professional web app using R.

First let’s understand basics of a Webpage

In general, web page contains the following section of details.

  1. Content (Header, Paragraph, Footer, Listing)

  2. Font style, color, background, border

  3. Images and Videos

  4. Popups, widgets, special effects etc.

HTML, CSS and JavaScript

These 3 web programming languages in conjunction  take care of all the information webpage contains (from text to adding special effects).

  1. HTML determines the content and structure of a page (header, paragraph, footer etc.)

  2. CSS controls how webpage would look like (color, font type, border etc.)

  3. JavaScript decides advanced behaviors such as pop-up, animation etc.

Fundamentals of Webpage

One of the most common web development term you should know : rendering. It is the act of putting together a web page for presentation.

Shiny Dashboard Syntax

In this section, I am using syntax of shinydashboard library. The structure of shinydashboard syntax is similar to shiny library. Both requires ui and server components. However, functions are totally different. Refer the code below. Make sure to install library before using the following program.

User Interfaceui = dashboardPage(dashboardHeader(title = “Blank Shiny App”),dashboardSidebar(),dashboardBody() )

Serverserver = function(input, output) { }

Run ApprunApp(list(ui = ui, server = server), launch.browser =T)

Example : Create Animation Effect

The program below generates animation in the web page. To test it, you can check out this link. When user hits “Click Me” button, it will trigger demojs() JavaScript which will initiate animation. It’s a very basic animation. You can edit the code and make it as complex as you want.

CSS

#myContainer {width: 400px;height: 400px;position: relative;background: black;}

JS

There are several ways to include custom JavaScript and CSS codes in Shiny. Some of the common ones are listed below with detailed explanation –

Method I : Use tags to insert HTML, CSS and JS Code in Shiny

HTML

tags$body(HTML(“Your HTML Code“))

CSS

tags$head(HTML(“”))

OR**CSS code can also be defined using **tags$style. 

tags$head(tags$style(HTML(” Your CSS Code “)))

JS

tags$head(HTML(“”))

OR**JS code can be described with **tags$script.

tags$head(tags$script(HTML(” Your JS Code “)))

Code specified in tags$head means it will be included and executed under ` . Similarly tags$body can also be used to make shiny run code within `

tags$head vs. tags$body

In general, JavaScript and CSS files are defined inside ** **

Animation Code in Shiny

“)), # HTML Code box(tags$body(HTML(“

Click Me

“)), height = 400) )) server = function(input, output) { } runApp(list(ui = ui, server = server), launch.browser =T)

Important Note

In JS, CSS and HTML code, make sure to replace double quotation mark with single quotation mark under shiny’s HTML(” “) function as it considers double quotation mark as closing the function.

Method II : Call JavaScript and CSS files in Shiny

You can use ` includeScript( ) ` and includeCSS( ) functions to refer JS and CSS codes from files saved in your local directory. You can save the files anywhere and mention the file location of them in the functions.

How to create JS and CSS files manually

Open notepad and paste JS code and save it with .js file extension and file type “All files” (not text document). Similarly you can create css file using .css file extension.

library(shinydashboard) # User Interface ui <- dashboardPage( dashboardHeader(title = “Basic Use of JS and CSS”), dashboardSidebar(), dashboardBody( # Call Javasript and CSS Code from file tags$head( includeScript(“C:\Users\DELL\Documents\animate.js”), includeCSS(“C:\Users\DELL\Documents\animation.css”) ), # HTML Code box(tags$body(HTML(“

Click Me

“)), height = 400) )) server = function(input, output) { } runApp(list(ui = ui, server = server), launch.browser =T)

When to use Method 2?

When you want to include a big (lengthy) JS / CSS code, use method 2. Method 1 should be used for small code snippets as RStudio does not support coloring and error-checking of JS / CSS code. Also it makes code unnecessary lengthy which makes difficult to maintain.

Method III : Add JS and CSS files under www directory

Step 1 : Create an app using shinyApp( ) function and save it as app.R. Refer the code below.**library(shinydashboard) library(shinydashboard) app <- shinyApp( ui <- dashboardPage( dashboardHeader(title = “Basic Use of JS”), dashboardSidebar(), dashboardBody( # Javasript and CSS Code tags$head(tags$script(src=”animate.js”)), tags$head(tags$link(rel=”stylesheet”, type = “text/css”, href = “animation.css”)), # HTML Code box(tags$body(HTML(“

Click Me

“)), height = 400) )) , server = function(input, output) { } )

Step 2 :Create a folder named www in your app directory (where your app app.r file is stored) and save .js and .css files under the folder. Refer the folder structure below.

Step 3 :**Submit runApp( ) **function. Specify path of app directory.

runApp(appDir = “C:/Users/DELL/Documents”, launch.browser = T)

Deepanshu founded ListenData with a simple objective – Make analytics easy to understand and follow. He has over 7 years of experience in data science and predictive modeling. During his tenure, he has worked with global clients in various domains.

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