Overload

Simple JavaScript Method Overloading

Usage

You can create a new function that takes overloaded calls by definining what those calls should accept by type.

Here is an example of usage:

var user = new Overload({
    // Get user name and data
    "": function () {
        return {
            "name": this._name,
            "data": this._data
        };
    },

    // Set user name
    "string": function (name) {
        this._name = name;
    },

    // Set user data
    "object": function (data) {
        this._data = data;
    },

    // Set user name and data
    "string, object": function (name, data) {
        this._name = name;
        this._data = data;
    },

    // Take arbitrary number of exta arguments
    "string, object, ...": function () {
        // Can access arguments through the "arguments" object
        console.log(arguments);
    },

    // Take any type as an argument
    "string, *, object": function () {
        console.log(arguments);
    }
});

Shared Main Method

Your overloaded functions support calling a primary function that will handle all variations of your funtion signatures. This allows you to write a single piece of logic that all overloaded functions can call to reduce code replication.

Here is an example from ForerunnerDB's Collection class:

Core.prototype.collection = new Overload({
	/**
	 * Get a collection by name. If the collection does not already exist
	 * then one is created for that name automatically.
	 * @param {Object} options An options object.
	 * @returns {Collection}
	 */
	'object': function (options) {
		return this.$main.call(this, options);
	},

	/**
	 * Get a collection by name. If the collection does not already exist
	 * then one is created for that name automatically.
	 * @param {String} collectionName The name of the collection.
	 * @returns {Collection}
	 */
	'string': function (collectionName) {
		return this.$main.call(this, {
			name: collectionName
		});
	},

	/**
	 * Get a collection by name. If the collection does not already exist
	 * then one is created for that name automatically.
	 * @param {String} collectionName The name of the collection.
	 * @param {String} primaryKey Optional primary key to specify the primary key field on the collection
	 * objects. Defaults to "_id".
	 * @returns {Collection}
	 */
	'string, string': function (collectionName, primaryKey) {
		return this.$main.call(this, {
			name: collectionName,
			primaryKey: primaryKey
		});
	},

	/**
	 * Get a collection by name. If the collection does not already exist
	 * then one is created for that name automatically.
	 * @param {String} collectionName The name of the collection.
	 * @param {Object} options An options object.
	 * @returns {Collection}
	 */
	'string, object': function (collectionName, options) {
		options.name = collectionName;

		return this.$main.call(this, options);
	},

	/**
	 * Get a collection by name. If the collection does not already exist
	 * then one is created for that name automatically.
	 * @param {String} collectionName The name of the collection.
	 * @param {String} primaryKey Optional primary key to specify the primary key field on the collection
	 * objects. Defaults to "_id".
	 * @param {Object} options An options object.
	 * @returns {Collection}
	 */
	'string, string, object': function (collectionName, primaryKey, options) {
		options.name = collectionName;
		options.primaryKey = primaryKey;

		return this.$main.call(this, options);
	},

	/**
	 * The main handler method. This get's called by all the other variants and
	 * handles the actual logic of the overloaded method.
	 * @param {Object} options An options object.
	 * @returns {*}
	 */
	'$main': function (options) {
		var name = options.name;

		if (name) {
			if (!this._collection[name]) {
				if (options && options.autoCreate === false) {
					throw('ForerunnerDB.Core "' + this.name() + '": Cannot get collection ' + name + ' because it does not exist and auto-create has been disabled!');
				}

				if (this.debug()) {
					console.log('Creating collection ' + name);
				}
			}

			this._collection[name] = this._collection[name] || new Collection(name).db(this);

			if (options.primaryKey !== undefined) {
				this._collection[name].primaryKey(options.primaryKey);
			}

			return this._collection[name];
		} else {
			throw('ForerunnerDB.Core "' + this.name() + '": Cannot get collection with undefined name!');
		}
	}
});

Notice that the defined $main function can be referenced from each of the overloaded functions via this.$main().