WindowEventHandlers.onbeforeprint

The onbeforeprint property of the WindowEventHandlers mixin is the EventHandler for processing beforeprint events for the current window. These events are raised before the print dialog window is opened.

The beforeprint and afterprint events allow pages to change their content before printing starts (perhaps to remove a banner, for example) and then revert those changes after printing has completed. In general, you should prefer the use of an @media print CSS at-rule, but it may be necessary to use these events in some cases.

Syntax

window.addEventListener("beforeprint", function(event) { ... });
window.onbeforeprint = function(event) { ... };

Polyfill

Safari does not implement these events, but you can create an equivalent result to the beforeprint event with window.matchMedia('print').

var mediaQueryList = window.matchMedia('print');
mediaQueryList.addListener(function(mql) {
  if(mql.matches) {
    console.log('webkit equivalent of onbeforeprint');
  }
});

Specification

Browser compatibility

See also

• Window.print()
• WindowEventHandlers.onafterprint
• Printing