19. The computing system of claim 15 , wherein the computer readable instructions comprise a web browser that notifies the event handler method of the first web component when the second web component fires the event.
15. A computing system comprising: at least one processing unit; and at least one computer readable storage media storing computer readable instructions which, when executed by the at least one processing unit, cause the at least one processing unit to: obtain multiple web components, the multiple web components including at least a first web component encapsulating first data and first code and a second web component encapsulating second data and second code; and execute a web application comprising the multiple web components by: providing separate isolated execution environments for the multiple web components, the separate isolated execution environments including at least a first isolated execution environment for the first web component and a second isolated execution environment for the second web component, receiving a request to register an event handler method of the first web component to respond to an event fired by the second web component; determining that the second web component has fired the event while executing within the second isolated execution environment, and causing the first web component to execute the event handler method within the first isolated execution environment responsive to the event being fired by the second web component.