Generic Local Storage Class

local-storage.ts

    /**
     * Customized HTML5 local storage class with additional functionality.
     */
    export class LocalStorage {
        /**
         * Checks if the browser supports local storage.
         * @returns true if the local storage is supported; false otherwise.
         */
        public static isSupported(): boolean {
            try {
                // Try to use basic methods of localStorage. 
                localStorage.setItem('__localstorage_support_test__', '');
                localStorage.getItem('__localstorage_support_test__');
                localStorage.removeItem('__localstorage_support_test__');
            } catch (e) {
                // If exception is thrown, then there is problem in local storage support.
                console.warn('LocalStorage Not supported for this browser.');
                return false;
            }

            // local storage is suuported.
            return true;
        };

        /**
         * Sets an encoded string item in the local storage.
         * @param key Key of the item to be stored.
         * @param value Value of the item to be stored.
         */
        public static setItem(key: string, value: string): void {
            localStorage.setItem(key, value);
        };

        /**
         * Sets an encoded object item in the local storage.
         * @param key Key of the item to be stored.
         * @param value Value of the item to be stored.
         */
        public static setItemObject<T>(key: string, value: T): void {
            const json = JSON.stringify(value);
            this.setItem(key, json);
        };

        /**
         * Gets the decoded string item from the local storage.
         * @param key Key of the item to be retrieved.
         * @returns String value against the given key.
         */
        public static getItem(key: string): string {
            // Check if the value for the key exists in the storage.
            if (localStorage.getItem(key) === undefined || localStorage.getItem(key) === null) {
                return null;
            }

            // Get and return the value.
            const value = localStorage.getItem(key);
            return value;
        };

        /**
         * Gets the the decoded object item from the local storage.
         * @param key Key of the item to be retrieved.
         * @returns Object of type T against the given key.
         */
        public static getItemObject<T>(key: string): T {
            // Check if the value for given key is null.
            if (this.getItem(key) === null) {
                return null;
            }

            // Parse and return the JSON object.
            const value = this.getItem(key);
            return JSON.parse(value) as T;
        };

        public static removeItem(key: string): void {
            localStorage.removeItem(key);    
        }
    }; // End of class: LocalStorage