soderlind/plugin-customizer

/* global wp, jQuery */
/* exported PluginCustomizerBlankSlate */

var PluginCustomizerBlankSlate = (function( api, $ ) {
    'use strict';

    var component = {
        data: {
            queryParamName: null,
            queryParamValue: null
        }
    };

    /**
     * Initialize functionality.
     *
     * @param {object} args Args.
     * @param {string} args.queryParamName  Query param name.
     * @param {string} args.queryParamValue Query param value.
     * @returns {void}
     */
    component.init = function init( args ) {
        _.extend( component.data, args );
        if ( ! args || ! args.queryParamName || ! args.queryParamValue ) {
            throw new Error( 'Missing args' );
        }

        api.bind( 'ready', function() {
            component.injectPreviewUrlQueryParam();
        } );
    };

    /**
     * Make sure that all previewed URLs include the customize_blank_slate query param.
     *
     * @returns {void}
     */
    component.injectPreviewUrlQueryParam = function injectPreviewUrlQueryParam() {
        var previousValidate = api.previewer.previewUrl.validate;
        api.previewer.previewUrl.validate = function injectQueryParam( url ) {
            var queryString, queryParams = {}, urlParser, validatedUrl;
            validatedUrl = previousValidate.call( this, url );

            // Parse the query params.
            urlParser = document.createElement( 'a' );
            urlParser.href = validatedUrl;
            queryString = urlParser.search.substr( 1 );
            _.each( queryString.split( '&' ), function( pair ) {
                var parts = pair.split( '=', 2 );
                if ( parts[0] ) {
                    queryParams[ decodeURIComponent( parts[0] ) ] = _.isUndefined( parts[1] ) ? null : decodeURIComponent( parts[1] );
                }
            } );

            // Amend the query param if not present.
            if ( component.data.queryParamValue !== queryParams[ component.data.queryParamName ] ) {
                queryParams[ component.data.queryParamName ] = component.data.queryParamValue;
                urlParser.search = $.param( queryParams );
                validatedUrl = urlParser.href;
            }
            return validatedUrl;
        };
    };

    return component;

}( wp.customize, jQuery ) );