Hi, there's a difference in the JavaScript you use for web pages, AcroForms (= static PDF forms created with Adobe Acrobat) and XFA forms (static or dynamic forms created with AEM Forms/LiveCycle Designer).
Acrobats scripting API uses a JavaScript subset of ECMAScript 262 5th edition. There's a reference manual available, that explians the Adobe-specific methods of this API. All other methods are explained online.
Acrobat JavaScript Scripting Reference: https://www.adobe.com/content/dam/acom/en/devnet/acrobat/pdfs/AcrobatDC_js_api_reference.pdf
LiveCycle in addition has another JavaScript- and also a FormCalc-API.
LiveCycle Scripting Basics: https://helpx.adobe.com/pdf/aem-forms/6-2/scripting-basics.pdf
LiveCylce Scripting Reference: https://helpx.adobe.com/pdf/aem-forms/6-2/scripting-reference.pdf
FormCalc reference: https://helpx.adobe.com/pdf/aem-forms/6-2/formcalc-reference.pdf
Hope this helps.
