iD/js/id/modes/add_point.js

iD.modes.AddPoint = function() {
    var mode = {
        id: 'add-point',
        title: 'Point',
        description: 'Restaurants, monuments, and postal boxes are points.'
    };

    var behavior;

    mode.enter = function() {
        var map = mode.map,
            surface = map.surface,
            history = mode.history,
            controller = mode.controller;

        map.tail('Click on the map to add a point.', true);

        function add() {
            var node = iD.Node({loc: map.mouseCoordinates()});

            history.perform(
                iD.actions.AddNode(node),
                'added a point');

            controller.enter(iD.modes.Select(node, true));
        }

        function cancel() {
            controller.exit();
        }

        behavior = iD.behavior.Draw()
            .on('add', add)
            .on('cancel', cancel)
            .on('finish', cancel)
            (surface);
    };

    mode.exit = function() {
        var map = mode.map,
            surface = map.surface;

        map.tail(false);
        behavior.off(surface);
    };

    return mode;
};