Simple helper module on TypeScript for using local storage (HTML5) in browser. Also have the class to store the list of emails that need to use for autocomplete in the some pages.

StorageHelper.ts

// module with classes and logic for working with local storage in browsers via JavaScript
// see also: http://professorweb.ru/my/html/html5/level5/5_1.php
module StorageHelper {
    export interface IStorageItem {
        key: string;
        value: any;
    }

    export class StorageItem {
        key: string;
        value: any;

        constructor(data: IStorageItem) {
            this.key = data.key;
            this.value = data.value;
        }
    }

    // class for working with local storage in browser (common that can use other classes for store some data)
    export class LocalStorageWorker {
        localStorageSupported: boolean;

        constructor() {
            this.localStorageSupported = typeof window['localStorage'] != "undefined" && window['localStorage'] != null;
        }

        // add value to storage
        add(key: string, item: string) {
            if (this.localStorageSupported) {
                localStorage.setItem(key, item);
            }
        }

        // get all values from storage (all items)
        getAllItems(): Array<StorageItem> {
            var list = new Array<StorageItem>();

            for (var i = 0; i < localStorage.length; i++) {
                var key = localStorage.key(i);
                var value = localStorage.getItem(key);

                list.push(new StorageItem({
                    key: key,
                    value: value
                }));
            }

            return list;
        }

        // get only all values from localStorage
        getAllValues(): Array<any> {
            var list = new Array<any>();

            for (var i = 0; i < localStorage.length; i++) {
                var key = localStorage.key(i);
                var value = localStorage.getItem(key);

                list.push(value);
            }

            return list;
        }

        // get one item by key from storage
        get(key: string): string {
            if (this.localStorageSupported) {
                var item = localStorage.getItem(key);
                return item;
            } else {
                return null;
            }
        }

        // remove value from storage
        remove(key: string) {
            if (this.localStorageSupported) {
                localStorage.removeItem(key);
            }
        }

        // clear storage (remove all items from it)
        clear() {
            if (this.localStorageSupported) {
                localStorage.clear();
            }
        }
    }

    // custom class for store emails in local storage
    export class EmailStorage {
        storageWorker: LocalStorageWorker;

        // main key that use for store list of emails
        storageKey: string;

        // list of emails
        addresses: Array<string>;

        constructor(storageKey: string) {
            this.storageWorker = new LocalStorageWorker();

            this.storageKey = storageKey;

            this.addresses = new Array<string>();

            this.activate();
        }

        // activate custom storage for emails
        activate() {
            //this.clear();

            this.loadAll();
        }

        // load all emails from storage to list for working with it
        loadAll() {
            var storageData = this.storageWorker.get(this.storageKey);

            if (storageData != null && storageData.length > 0) {
                var emails = JSON.parse(storageData);
                console.log(emails);
                if (emails != null) {
                    this.addresses = emails;
                }
                console.log(this.addresses);
            }
        }

        // add new email (without duplicate)
        addEmail(email: string) {
            if (email.length > 0) {

                // 1. Split email addresses if needed (if we get list of emails)
                var mas = email.split(/,|;/g);
                //console.log(mas);

                // 2. Add each email in the splited list
                for (var i = 0; i < mas.length; i++) {
                    // check if not exist and not add new (duplicate)
                    var index = this.addresses.indexOf(mas[i].trim());
                    if (index < 0) {
                        this.addresses.push(mas[i].trim());
                    }
                }

                console.log(this.addresses);

                // 3. save to storage
                this.save();
            }
        }

        // clear all data about emails
        clear() {
            // remove data by key from storage
            this.storageWorker.add(this.storageKey, "");

            // or remove with key
            //this.storageWorker.remove(this.storageKey);
        }

        // save to storage (save as JSON string)
        save() {
            var jsonEmails = JSON.stringify(this.addresses);
            this.storageWorker.add(this.storageKey, jsonEmails);
        }
    }
} 

I am copying a part of code from this