storage.js

/*!
 * Copyright 2018 The Rust Project Developers. See the COPYRIGHT
 * file at the top-level directory of this distribution and at
 * http://rust-lang.org/COPYRIGHT.
 *
 * Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
 * http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
 * <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
 * option. This file may not be copied, modified, or distributed
 * except according to those terms.
 */

var currentTheme = document.getElementById("themeStyle");
var mainTheme = document.getElementById("mainThemeStyle");

function updateLocalStorage(name, value) {
    if (typeof(Storage) !== "undefined") {
        localStorage[name] = value;
    } else {
        // No Web Storage support so we do nothing
    }
}

function getCurrentValue(name) {
    if (typeof(Storage) !== "undefined" && localStorage[name] !== undefined) {
        return localStorage[name];
    }
    return null;
}

function switchTheme(styleElem, mainStyleElem, newTheme) {
    styleElem.href = mainStyleElem.href.replace("rustdoc.css", newTheme + ".css");
    updateLocalStorage('theme', newTheme);
}

switchTheme(currentTheme, mainTheme, getCurrentValue('theme') || 'main');