Local storage with Cookie fallback

local_storage_fallback.js

/**
 * Simple localStorage with Cookie Fallback
 *
 * USAGE:
 * ----------------------------------------
 * Set New / Modify:
 *   store('my_key', 'some_value');
 *
 * Retrieve:
 *   store('my_key');
 *
 * Delete / Remove:
 *   store('my_key', null);
 */
var store = function store(key, value) {

   var lsSupport = false;

   function storageAvailable(type) {
        try {
            var storage = window[type],
                x = '__storage_test__';
            storage.setItem(x, x);
            storage.removeItem(x);
            return true;
        }
        catch(e) {
            return false;
        }
    }
    if (storageAvailable('localStorage')) {
        // Yippee! We can use localStorage awesomeness
        console.log(`Using local storage`);
        lsSupport = true;
    } else {
        console.log(`Using cookie storage`);
    }


    // If value is detected, set new or modify store
    if (typeof value !== "undefined" && value !== null) {
        // Convert object values to JSON
        if ( typeof value === 'object' ) {
            value = JSON.stringify(value);
        }
        // Set the store
        if (lsSupport) { // Native support
            localStorage.setItem(key, value);
        } else { // Use Cookie
            createCookie(key, value, 30);
        }
    }
    
    // No value supplied, return value
    if (typeof value === "undefined") {
        // Get value
        if (lsSupport) { // Native support
            data = localStorage.getItem(key);
        } else { // Use cookie 
            data = readCookie(key);
        }
        
        // Try to parse JSON...
        try {
           data = JSON.parse(data);
        }
        catch(e) {
           data = data;
        }
        
        return data;
    }
    
    // Null specified, remove store
    if (value === null) {
        if (lsSupport) { // Native support
            localStorage.removeItem(key);
        } else { // Use cookie
            createCookie(key, '', -1);
        }
    }


    /**
     * Creates new cookie or removes cookie with negative expiration
     * @param  key       The key or identifier for the store
     * @param  value     Contents of the store
     * @param  exp       Expiration - creation defaults to 30 days
     */
    function createCookie(key, value, exp) {
        var date = new Date();
        date.setTime(date.getTime() + (exp * 24 * 60 * 60 * 1000));
        var expires = "; expires=" + date.toGMTString();
        document.cookie = key + "=" + value + expires + "; path=/";
    }
    
    /**
     * Returns contents of cookie
     * @param  key       The key or identifier for the store
     */
    function readCookie(key) {
        var nameEQ = key + "=";
        var ca = document.cookie.split(';');
        for (var i = 0, max = ca.length; i < max; i++) {
            var c = ca[i];
            while (c.charAt(0) === ' ') c = c.substring(1, c.length);
            if (c.indexOf(nameEQ) === 0) return c.substring(nameEQ.length, c.length);
        }
        return null;
    }

}