onCallback
Stability: EXPERIMENTAL
Introduced: PhantomJS 1.6
This callback is invoked when there is a JavaScript window.callPhantom call made on the web page. The only argument passed to the callback is a data object.
Note: window.callPhantom is still an experimental API. In the near future, it will be likely replaced with a message-based solution which will still provide the same functionality.
Although there are many possible use cases for this inversion of control, the primary one so far is to prevent the need for a PhantomJS script to be continually polling for some variable on the web page.
Examples
Send data from client to server
WebPage (client-side)
if (typeof window.callPhantom === 'function') {
window.callPhantom({ hello: 'world' });
}
PhantomJS (server-side)
var webPage = require('webpage');
var page = webPage.create();
page.onCallback = function(data) {
console.log('CALLBACK: ' + JSON.stringify(data));
// Prints 'CALLBACK: { "hello": "world" }'
};
Send data from client to server then back again
WebPage (client-side)
if (typeof window.callPhantom === 'function') {
var status = window.callPhantom({
secret: 'ghostly'
});
alert(status);
// Prints either 'Accepted.' or 'DENIED!'
}
PhantomJS (server-side)
var webPage = require('webpage');
var page = webPage.create();
page.onCallback = function(data) {
if (data && data.secret && (data.secret === 'ghostly')) {
return 'Accepted.';
}
return 'DENIED!';
};
Allow web page Javascript to close PhantomJS
This can be helpful when the web page running in PhantomJS needs to exit PhantomJS.
WebPage (client-side)
if (typeof window.callPhantom === 'function') {
var status = window.callPhantom({
command: 'exit',
reason: 'User Request.'
});
}
PhantomJS (server-side)
var webPage = require('webpage');
var page = webPage.create();
page.onCallback = function(data) {
if (data && data.command && (data.command === 'exit')) {
if (data.reason) console.log('web page requested exit: '+data.reason);
phantom.exit(0);
}
};