Factory with composition

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‘Prefer composition over inheritance’ is an important and popular programming principle, used to assign behaviors to objects, as opposed to inheriting many often unneeded behaviors.

Behaviour factories

var speaker = function (state) {
    var noise = state.noise || 'grunt';

    return {
        speak: function () {
            console.log(state.name + ' says ' + noise);
        }
    };
};

var mover = function (state) {
    return {
        moveSlowly: function () {
            console.log(state.name + ' is moving slowly');
        },
        moveQuickly: function () {
            console.log(state.name + ' is moving quickly');
        }
    };
};

Object factories

var person = function (name, age) {
    var state = {
        name: name,
        age: age,
        noise: 'Hello'
    };

    return Object.assign(     // Merge our 'behaviour' objects
        {},
        speaker(state),
        mover(state)
    );
};

var rabbit = function (name, colour) {
    var state = {
        name: name,
        colour: colour
    };

    return Object.assign(
        {},
        mover(state)
    );
};

Usage

var fred = person('Fred', 42);
fred.speak();        // outputs: Fred says Hello
fred.moveSlowly();   // outputs: Fred is moving slowly

var snowy = rabbit('Snowy', 'white');
snowy.moveSlowly();  // outputs: Snowy is moving slowly
snowy.moveQuickly(); // outputs: Snowy is moving quickly
snowy.speak();       // ERROR: snowy.speak is not a function

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Design patterns:
* Factory with composition

Table Of Contents
11 Arrays
12 Objects
14 Classes
16 Map
17 Set
24 Loops
27 Date
29 Scope
30 AJAX
35 Cookies
41 JSON
44 Fetch
45 Modules
46 Screen
59 Design patterns
64 Console
68 Symbols
73 Modals
76 Events
86 Proxy
89 WeakMap
90 WeakSet
102 Tilde