Overlode

Javascript function overloading overloding utility. This utility's peculiar interface will make overloding functions easier for you.

Quick Start

Installing with npm.

> npm install overlode

Or download the source file overlode.js.

Write your first overloded function. Here we are using rubric.js to help with checks.

var overlode = require('overlode');
var rubric = require('rubric');

var createUser = overlode(

    // create a user using data passed in as an object, and a callback function
    [ rubric.obj, rubric.fn ],
    function (data, callback) {

    },

    // create a user using data passed in as arguments, and a callback function
    [ rubric.str.range(1, 50), rubric.str.range(1, 50), rubric.fn ],
    function (firstName, lastName, callback) {

    },

    // default action, if no overlode is satisfied
    function () {
        throw new Error('Oops, incorrect usage of createUser()!');
    }
);

createUser({ first: 'Joe', last: 'Doe' }, function () { }); // triggers the 1st overlode
createUser('Joe', 'Doe', function () {}); // triggers the 2nd overlode
createUser(function () {}, 'Joe', 'Doe'); // triggers the 3rd (default) overlode

Supported Tests

overlode(
    // FUNCTION
    // Value is evaluated by a function, function must return true or false
    [ function (arg) { return true; } ],
    function action (arg) {},

    // OBJECT
    // Value must be of the same object type
    [ new Thing ],
    function action (thing) {},

    // WILDCARD
    // Value can be anything
    [ '*' ],
    function action (widlcard) {},

    // NUMBER
    // number of arguments == number of arguments used == number
    3,
    function action (arg1, arg2, arg3) {},

    // EMPTY ARRAY
    // No tests, no args, no required args
    [ ],
    function action () {},
);

Design Pattern

Good!

overlode(
    // tests and actions come in pairs
    [ test, test, test ],
    function action (arg, arg, arg) {},

    // number of tests match number of arguments taken by action
    [ test, test ],
    function action (arg, arg) {},

    // last function is the default and gets ran if no other ones are triggered
    function default () {}
);

Function overlodes should always come in pairs in this order: array and function. The array should contain the tests for the arguments of the overlode, and the function is the function to use if the tests are satisfied.

Bad :(

overlode(
    [ test, test, test ], // never used
    [ test, test ],
    function action (arg, arg) {}
);

Overlodes will be tested in the order they are written, from the top to the bottom. Whenever an array of tests pass it will try to run the function immediately afterwards. If it can't (not a funtion) it will reset and look for another test, and then another function.

Bad :(

overlode(
    [ test, test, test ],
    function action (arg, arg, arg) {},
    function action (arg, arg, arg) {}, // never used

    [ test, test ],
    function action (arg, arg) {},

    function default () {} // default action
);

If 2 functions are right after each other, the second function will be ignored as there are no tests preceding it. Unless, the function is the last argument in the overlode, in which case it is considered the default action and will be run if no other overlodes are run.

Bad :(

overlode(
    [ test1, test2, test3 ],
    function action (arg1) {}, // never used
);

The number of tests should always match the number of arguments an action takes. Otherwise, the action will never get ran because tests will always fail.