In terms of features, both javaScriptProxy and javaScriptProxy can inject a JavaScript object into a window object and call the method of the object in the window object.
In terms of APIs, javaScriptProxy is a method of the Web component, and registerJavaScriptProxy is a method of the WebviewController.
In terms of registered objects, the former can register only one object, and the latter can register multiple objects.
In terms of the lifecycle, javaScriptProxy is called during Web component initialization, and registerJavaScriptProxy is called after Web component initialization.
For details, see javaScriptProxy and registerJavaScriptProxy.