onAlert
Introduced: PhantomJS 1.0
This callback is invoked when there is a JavaScript alert on the web page. The only argument passed to the callback is the string for the message. There is no return value expected from the callback handler.
Examples
var webPage = require('webpage');
var page = webPage.create();
page.onAlert = function(msg) {
console.log('ALERT: ' + msg);
};