brotherton-erpnext/erpnext/docs/user/manual/en/customize-erpnext/custom-scripts/custom-script-examples/custom-button.md

Add a Custom Button

frappe.ui.form.on("Event", "refresh", function(frm) {
	frm.add_custom_button(__("Do Something"), function() {
		// When this button is clicked, do this
		
		var subject = frm.doc.subject;
		var event_type = frm.doc.event_type;
		
		// do something with these values, like an ajax request 
		// or call a server side frappe function using frappe.call
		$.ajax({
			url: "http://example.com/just-do-it",
			data: {
				"subject": subject,
				"event_type": event_type
			}
			
			// read more about $.ajax syntax at http://api.jquery.com/jquery.ajax/
		
		});
	});
});