@nathanfaucett/storage/src/index.js

local storage polyfill

var has = require("@nathanfaucett/has"),
    emptyFunction = require("@nathanfaucett/empty_function"),
    isNullOrUndefined = require("@nathanfaucett/is_null_or_undefined"),
    environment = require("@nathanfaucett/environment");

var storage = exports,
    window = environment.window,
    supportsStorage = (function() {
        try {
            return (
                "localStorage" in window &&
                !isNullOrUndefined(window.localStorage)
            );
        } catch (e) {
            return false;
        }
    })(),
    localStorage,
    storageGet,
    storageHas,
    storageSet,
    storageRemove,
    storageClear,
    storageIsNative;

if (supportsStorage) {
    localStorage = window.localStorage;

    storageHas = function(key) {
        return !isNullOrUndefined(localStorage.getItem(key));
    };

    storageGet = function(key) {
        return localStorage.getItem(key);
    };

    storageSet = function(key, value) {
        localStorage.setItem(key, value);
    };

    storageRemove = function(key) {
        return localStorage.removeItem(key);
    };

    storageClear = function() {
        return localStorage.clear();
    };

    storageIsNative = emptyFunction.thatReturnsTrue;
} else {
    localStorage =
        global.__LOCAL_STORAGE_POLYFILL__ ||
        (global.__LOCAL_STORAGE_POLYFILL__ = {});

    storageHas = function(key) {
        return !isNullOrUndefined(localStorage[key]);
    };

    storageGet = function(key) {
        var item = localStorage[key];

        if (isNullOrUndefined(item)) {
            return null;
        } else {
            return item;
        }
    };

    storageSet = function(key, value) {
        localStorage[key] =
            value && value.toString ? value.toString() : value + "";
    };

    storageRemove = function(key) {
        return delete localStorage[key];
    };

    storageClear = function() {
        var key;

        for (key in localStorage) {
            if (has(localStorage, key)) {
                delete localStorage[key];
            }
        }
    };

    storageIsNative = emptyFunction.thatReturnsFalse;
}

storage.has = storageHas;
storage.get = storageGet;
storage.set = storageSet;
storage.remove = storageRemove;
storage.clear = storageClear;
storage.isNative = storageIsNative;