Simple Britecharts interactor plugin

interactors.js

define(function(require) {

    const d3Selection = require('d3-selection');

    /**
     * Toggles selection on clickable elements. Will set classes "selected" and "dimmed".
     * @param  {Number} selector A valid selector of the elements to toggle
     * @example
     * barChart.on('customClick', britecharts.interactors.multiToggle('rect.bar'))
     *
     * @return {void}
     */

     function multiToggle(selector) {
        return function() {
            const that = this;
            let hasSelection = false;
            const selection = d3Selection.select(this.farthestViewportElement)
                .selectAll(selector);

            selection.classed('selected', function(){
                const isSelected = this.classList.contains('selected');
                const shouldBeSelected = this === that ? !isSelected : isSelected;

                hasSelection = hasSelection || shouldBeSelected;
                return shouldBeSelected;
            });
            selection.classed('dimmed', function(){
                return hasSelection && !this.classList.contains('selected');
            });
        }
    }

    return {
        multiToggle
    };
});