GM storage wrapper

simple wrapper for GM_storage with added functions

Dieses Skript sollte nicht direkt installiert werden. Es handelt sich hier um eine Bibliothek für andere Skripte, welche über folgenden Befehl in den Metadaten eines Skriptes eingebunden wird // @require https://update.greasyfork.org/scripts/38717/253024/GM%20storage%20wrapper.js

/*jshint esversion: 6 */
// ==UserScript==
// @name           GM storage wrapper
// @version        1.0
// @description    simple wrapper for GM_storage with added functions
// ==/UserScript==

    var gmStorageWrapper = {
        options : {
            prefix : ''
        },
        // “Set” means “add if absent, replace if present.”
        set : function(key, value) {
            let storageVals = this.read(key);

            if (typeof storageVals === 'undefined' || !storageVals) {
                // add if absent
                return this.add(key, value);
            } else {
                // replace if present
                this.write(key, value);
                return true;
            }
        },
        // “Add” means “add if absent, do nothing if present” (if a uniquing collection).
        add : function(key, value) {
            let storageVals = this.read(key, false);

            if (typeof storageVals === 'undefined' || !storageVals) {
                this.write(key, value);
                return true;
            } else {
                if (this._isArray(storageVals)) { // is array
                    let index = storageVals.indexOf(value);

                    if (index !== -1) {
                        // do nothing if present
                        return false;
                    } else {
                        // add if absent
                        storageVals.push(value);
                        this.write(key, storageVals);
                        return true;
                    }
                } else if (this._isObject(storageVals)) { // is object
                    // merge obj value on obj
                    let result,
                        objToMerge = value;

                    result = Object.assign(storageVals, objToMerge);
                    this.write(key, result);
                    return false;
                }
                return false;
            }
        },
        // “Replace” means “replace if present, do nothing if absent.”
        replace : function(key, itemFind, itemReplacement) {
            let storageVals = this.read(key, false);

            if (typeof storageVals === 'undefined' || !storageVals) {
                // do nothing if absent
                return false;
            } else {
                if (this._isArray(storageVals)) { // is Array
                    let index = storageVals.indexOf(itemFind);

                    if (index !== -1) {
                        // replace if present
                        storageVals[index] = itemReplacement;
                        this.write(key, storageVals);
                        return true;
                    } else {
                        // do nothing if absent
                        return false;
                    }
                } else if (this._isObject(storageVals)) {
                    // is Object
                    // replace property's value
                    storageVals[itemFind] = itemReplacement;
                    this.write(key, storageVals);
                    return true;
                }
                return false;
            }
        },
        // “Remove” means “remove if present, do nothing if absent.”
        remove : function(key, value) {
            if (typeof value === 'undefined') { // remove key
                this.delete(key);
                return true;
            } else { // value present
                let storageVals = this.read(key);

                if (typeof storageVals === 'undefined' || !storageVals) {
                    return true;
                } else {
                    if (this._isArray(storageVals)) { // is Array
                        let index = storageVals.indexOf(value);

                        if (index !== -1) {
                            // remove if present
                            storageVals.splice(index, 1);
                            this.write(key, storageVals);
                            return true;
                        } else {
                            // do nothing if absent
                            return false;
                        }
                    } else if (this._isObject(storageVals)) { // is Object
                        let property = value;

                        delete storageVals[property];
                        this.write(key, storageVals);
                        return true;
                    }
                    return false;
                }
            }
        },
        get : function(key, defaultValue) {
            return this.read(key, defaultValue);
        },

        // GM storage API
        read : function(key, defaultValue) {
            return this.unserialize(GM_getValue(this._prefix(key), defaultValue));
        },
        write : function(key, value) {
            return GM_setValue(this._prefix(key), this.serialize(value));
        },
        delete : function(key) {
            return GM_deleteValue(this._prefix(key));
        },
        readKeys : function() {
            return GM_listValues();
        },
        // /GM Storage API

        getAll : function() {
            const keys = this._listKeys();
            let obj    = {};

            for (let i = 0, len = keys.length; i < len; i++) {
                obj[keys[i]] = this.read(keys[i]);
            }
            return obj;
        },
        getKeys : function() {
            return this._listKeys();
        },
        getPrefix : function() {
            return this.options.prefix;
        },

        empty : function() {
            const keys = this._listKeys();

            for (let i = 0, len = keys.lenght; i < len; i++) {
                this.delete(keys[i]);
            }
        },
        has : function(key) {
            return this.get(key) !== null;
        },
        forEach : function(callbackFunc) {
            const allContent = this.getAll();

            for (let prop in allContent) {
                callbackFunc(prop, allContent[prop]);
            }
        },
        unserialize : function(value) {
            if (this._isJson(value)) {
                return JSON.parse(value);
            }
            return value;
        },
        serialize : function(value) {
            if (this._isJson(value)) {
                return JSON.stringify(value);
            }
            return value;
        },
        _listKeys : function(usePrefix = false) {
            const prefixed = this.readKeys();
            let unprefixed = [];

            if (usePrefix) {
                return prefixed;
            } else {
                for (let i = 0, len = prefixed.length; i < len; i++) {
                    unprefixed[i] = this._unprefix(prefixed[i]);
                }
                return unprefixed;
            }
        },
        _prefix : function(key) {
            return this.options.prefix + key;
        },
        _unprefix : function(key) {
            return key.substring(this.options.prefix.length);
        },
        _isJson : function(item) {
            try {
                JSON.parse(item);
            } catch (e) {
                return false;
            }
            return true;
        },
        _isObject : function(a) {
            return (!!a) && (a.constructor === Object);
        },
        _isArray : function(a) {
            return (!!a) && (a.constructor === Array);
        }
    };