Example for using ENJOY.js multimethods

multimethods-example.js

var method = require("enjoy-js").method;
var specialize = require("enjoy-js").specialize;
var is_object = require("enjoy-js").is_object;
var is_string = require("enjoy-js").is_string;

// Defining a multimethod with a default implementation:

var hello = method(function () {
    return "Hello!";
});

// Adding some implementations to the multimethod:

specialize(hello, is_person, is_english, function (person) {
    return "Hello " + person.name + "!";
});

specialize(hello, is_person, is_german, function (person) {
    return "Guten Tag, " + person.name + "!";
});

specialize(hello, is_person, "ja_JP", function (person) {
    return "今日は, " + person.name + "さん！";
});

// Calling the multimethod:

console.log(hello()); // "Hello!"
console.log(hello(person("Pete"), "en_US")); // "Hello Pete!"
console.log(hello(person("Douglas"), "en_GB")); // "Hello Douglas!"
console.log(hello(person("Jonathan"), "de_DE")); // "Guten Tag, Jonathan!"


/* -------------------------
        Little helpers
   ------------------------- */

// Some predicate functions:

function is_person (thing) {
    return is_object(thing) && thing.type === "person";
}

function is_english (code) {
    return is_string(code) && code.match(/^en/);
}

function is_german (code) {
    return is_string(code) && code.match(/^de/);
}

// Function that creates persons:

function person (name) {
    return {
        type: "person",
        name: name
    };
}