contrast.service.js

/**
 * Created by klauskpm
 */
(function () {
    'use strict';

    app
        .factory('contrastService', ContrastService);

    ContrastService.$inject = ['storageService'];

    function ContrastService(storageService) {
        var storage = 'contrastState';
        var cssClass = 'contrast';

        var service = {
            currentState: null,
            checkState: checkContrast,
            getState: getContrastState,
            setState: setContrastState,
            toggleState: toggleContrast
        };

        window.toggleContrast = function() { service.toggleState() };

        return service;

        function checkContrast() {
            this.currentState = this.getState();

            updateView(this.currentState);
        }

        function getContrastState() {
            var state = storageService.get(storage);

            return !(typeof state === 'undefined' || !state);
        }

        function setContrastState(state) {
            storageService.set(storage, state);
            this.currentState = state;
            updateView(state);
        }

        function updateView(state) {
            var body = document.getElementsByTagName('body')[0];

            if (state)
                body.classList.add(cssClass);
            else
                body.classList.remove(cssClass);
        }

        function toggleContrast() {
            this.setState(!this.currentState);
        }
    }
})();