iD/js/id/behavior/select.js

iD.behavior.Select = function(context) {
    function click() {
        var datum = d3.select(d3.event.target).datum();
        if (datum instanceof iD.Entity) {
            if (d3.event.shiftKey) {
                context.enter(iD.modes.Select(context, context.selection().concat([datum.id])));
            } else {
                context.enter(iD.modes.Select(context, [datum.id]));
            }
        } else if (!d3.event.shiftKey) {
            context.enter(iD.modes.Browse(context));
        }
    }

    var behavior = function(selection) {
        selection.on('click.select', click);
    };

    behavior.off = function(selection) {
        selection.on('click.select', null);
    };

    return behavior;
};