In PDF workflows, forms provide not only a vehicle for data entry, but also field format and data validation, computation, and submission. For all of these behaviours, PDF forms technology relies on JavaScript.
Adobe Acrobat defines a set of custom JavaScript objects which deal with specifics of the Acrobat Viewer and PDF documents. These custom JavaScript objects collectively form the Acrobat Document Object Model (DOM) which allow client-side JavaScripts to directly interact with the program and documents. JavaScript documentation for desktop products resideshere.
For Acrobat Reader DC, JavaScript support includes performing build-in forms calculations, data validation, and data formatting. The JavaScript framework is general enough to support other JavaScript APIs in the future and it regularly evolves.