How to Access Data and Controls With JavaScript

To access data and controls of a form with JavaScript you have to use the Client API executionContext.

First get the formContext object.

var formContext = executionContext.getFormContext();

To access form data for example the value of the field firstname use the formContext.data.entity.attributes object.

var formContext = executionContext.getFormContext();
var firstName = formContext.data.entity.attributes.get("firstname").getValue();
// Or
var firstName = formContext.getAttribute("firstname").getValue();

To access the controls themselves for example to hide them use the formContext.ui.controls object.