Extending menu and toolbar

The module josm/ui/menu provides the class JSAction which can be used to create actions and add them to the JOSM menu and/or the JOSM toolbar.

var JSAction = require("josm/ui/menu").JSAction;
// create the action 
var action = new JSAction({
    name: "My Action",
    tooltip: "This is my action",
    onExecute: function() {
       josm.alert("MyAction: executing ...");
    }
});
// add it to the edit menu 
action.addToMenu(josm.menu.get("edit"));
// add it to the toolbar (append it at the end of the toolbar)
action.addToToolbar({at: "end"});