How to Use JavaScript in Displayr

This article outlines how to access and use JavaScript in Displayr.

Method

JavaScript is the scripting language of Displayr. It is used for:

Creating numeric or text variables:
- from the Data Sources tree by hovering over any variable > Plus (+) > Custom Code > JavaScript - Numeric / JavaScript - Text.
- from the toolbar via Anything > Data > Variables > New > Custom Code > JavaScript - Numeric / JavaScript - Text. See How to Create a Custom Numeric JavaScript Variable and How to Create a Custom JavaScript Text Variable.
Creating Rules:
- from the Data tab in the object inspector via Rules > Plus (+) > New custom rule (write your own JavaScript) > Edit JavaScript. See How to Create a Custom Rule.
Creating QScripts (for Enterprise users):
- from the toolbar via Anything > [Company name] > Open QScript Editor. See How to Create a Custom QScript.
Creating controls for R-based analysis tools:
- from the Data tab in the object inspector via Inputs Javascript. See How to Create User Input Fields in a Custom Analysis Tool.
Writing many of the functions available from in-app menus.

JavaScript versus R

Just like R variables, JavaScript variables are updated automatically in the project, and you can also easily go back to edit variables if you want to tweak the code.
JavaScript code is run through your browser and was originally designed as a scripting language for websites. R code, on the other hand, requires data to be packaged up and processed on our R servers and was specifically designed to do basic as well as advanced analysis.
While usually there isn't a noticeable difference between creating a basic JavaScript variable and an R variable, if your data is quite large (think hundreds of thousands of cases) and you're doing a simple calculation, it may be faster to use JavaScript.
Some advanced calculations may be easier - or only possible - to create using R.
JavaScript can only reference the Name of a variable, whereas R can reference the Name or Label.
JavaScript can only reference a single Variable at a time, whereas R can reference the Variable Set.
JavaScript is 0-based so the first iteration in a loop or array is 0, whereas in R it is 1.
R objects, such as Calculations, control boxes, and other Standard R outputs cannot be referenced using JavaScript.
When copying a variable over from a linked data set, it is often better to use JavaScript.

While all the standard functions are available in JavaScript, we have also created our own set of functions:

isNaN(variable_name) - Returns a 0 if the variable is not missing and a 1 if the variable is missing.
Q.AsNumeric(variable_name) - Converts a Text Variable containing numbers into a Numeric Variable.
Q.Label(variable_name) - Converts a variable's value into its corresponding label. e.g. for a Gender question, 2 would become Female.
Q.Source(variable_name) - Returns the original source value of a variable, ignoring any recoding or Exclude from Analyses settings.