Local-storage library functions

localstorage-helper-functions

/**
	This module contains all library function for localstorage usage
**/
var appLocalStorage = {

    /**
     * Checks if localstorage is supported on the current browser
     */
    hasStorage: function () {
        try {
            localStorage.setItem('test', '7');
            if (localStorage.getItem('test') === '7') {
                localStorage.removeItem('test');
                return true;
            }
        } catch (er) {}
        return false;
    },

    /**
     * Set's a key to localstorage. Overrides if already present
     * E.g. set("userid", "shivraj")
     * E.g. set({userid: "shivraj", lname: "rath"})
     */
    set: function (key, value) {
        try {
            if (typeof key === "object") {
                // There are multiple keys
                var keys = key;

                for (key in keys) {
                    if (keys.hasOwnProperty(key)) {
                        var value = key[key];
                        if (typeof value === "object") {
                            value = JSON.stringify(value);
                        }
                        localStorage.setItem(key, value);
                    }
                }

            } else {
                if (typeof value === "object") {
                    value = JSON.stringify(value);
                }
                localStorage.setItem(key, value);
            }
            return true;
        } catch (er) {
            return false;
        }
    },

    /**
     * Get's the value for a localstorage key. If no parameter is provided it returns all the values.
     * E.g: get("userid") or get(["userid", "fname"])
     */
    get: function (keys) {
        try {
            if (keys) {
                if (typeof keys === "object") {
                    var valObj = {};
                    for (var index in keys) {
                        if (keys.hasOwnProperty(index)) {
                            var key = keys[index];
                            if (typeof key === "string") {
                                var val = this.get(key);
                                valObj[key] = val;
                            }
                        }
                    }
                    return valObj;
                } else {
                    return localStorage.getItem(keys);
                }
            } else {
                return this.all();
            }
        } catch (er) {
            return false;
        }
    },

    /**
     * Removes a key from localstorage
     * @param  {[string/array]} keys
     * E.g: remove("userid") or remove(["userid", "lname"])
     * Returns the values removed
     */
    remove: function (keys) {
        try {
            var val;
            if (typeof keys === "object") {
                var removedVals = [];
                for (var index in keys) {
                    if (keys.hasOwnProperty(index)) {
                        var key = keys[index];
                        if (typeof key === "string") {
                            val = this.get(key);
                            localStorage.removeItem(key);
                            removedVals.push(val);
                        }
                    }
                }
                return removedVals;
            } else {
                val = this.get(keys);
                localStorage.removeItem(keys);
                return val;
            }
        } catch (er) {
            return false;
        }
    },

    /**
     * @return Returns a JSON object with all key value pair
     */
    all: function () {
        try {
            var i = 0,
                oJson = {},
                sKey;
            for (; i < localStorage.length; i++) {
                sKey = localStorage.key(i);
                oJson[sKey] = localStorage.getItem(sKey);
            }
            return oJson;
        } catch (er) {
            return false;
        }
    },

    /**
     * Clears all the localstorage values
     */
    clear: function () {
        try {
            localStorage.clear();
            return true;
        } catch (er) {
            return false;
        }
    },

    /**
     * @return {Boolean} Whether or not a key is present in localstorage
     */
    isKey: function (key) {
        try {
            if (localStorage.getItem(key)) {
                return true;
            }
            return false;
        } catch (er) {
            return false;
        }
    }
};

Updated with ability to accept multiple keys. JSLint verified.