| Parameter | Details | 
|---|---|
| eventOrMessage | Some browsers will call the event handler with just one argument, an Eventobject. However, other browsers, especially the older ones and older mobile ones will supply aStringmessage as a first argument. | 
| url | If a handler is called with more than 1 argument, the second argument usually is an URL of a JavaScript file that is the source of the problem. | 
| lineNumber | If a handler is called with more than 1 argument, the third argument is a line number inside the JavaScript source file. | 
| colNumber | If a handler is called with more than 1 argument, the fourth argument is the column number inside the JavaScript source file. | 
| error | If a handler is called with more than 1 argument, the fifth argument is sometimes an Errorobject describing the problem. | 
Unfortunately, window.onerror has historically been implemented differently by each vendor. The information provided in the Parameters section is an approximation of what to expect across different browsers and their versions.