Depending on the size of your data, the report function can run for several seconds or minutes, just like reports in the JasperReports Server UI. You can listen for events that give the status of running reports and let you display pages sooner.

This chapter contains the following sections:

Tracking Completion Status

By listening to the reportCompleted event, you can give information or take action when a report finishes rendering.

Listening to Page Totals

By listening to the changeTotalPages event, you can track the filling of the report.

Listening for the Last Page

By listening to the pageFinal event, you can know when the last page of a running report has been generated.

Customizing a Report's DOM Before Rendering

By listening to the beforeRender event, you can access the Document Object Model (DOM) of the report to view or modify it before it is displayed. In the example the listener finds span elements and adds a color style and an attribute my-attr="test" to each one.

The HTML page that displays the report uses a static list of reports in a drop-down selector, but otherwise needs only a container element. This is similar to the basic report example in Rendering a Report, except that the JavaScript above will change the report before it is displayed.