construct.js

Simple sugar for establishing prototype-based inheritance

construct.js is a javascript library that makes it easy to define inheritance. It doesn’t try to do anything fancy and just gives you an easy syntax for establishing prototypical inheritance.

It is debugging-friendly in that you really get back what you expect. Say you define a javascript constructor function; construct gives you back an object literally made with it. This means that when you inspect it in the console, the type name is properly in tact.

Note: After more research, js engines actually do a lot of work to tag function names correctly, so the foo: function() {} still actually gets tagged with foo. This library was intended to improve that, but it actually doesn’t offer much over the normal syntax.

This depends on Object.create and prototype.constructor.name and I’m still researching the browser compatibility of them.

You can view examples in the examples directory, but here’s a taste:

// shape.js

// This is the preferred structure of defining classes. Just list
// normal functions and tie them together into a class at the end.

function Shape(x, y) {
    this.x = x;
    this.y = y;
}

function move(dx) {
    this.x += dx || 5;
}

function render() {
    var x = this.x;
    var y = this.y;
    console.log("shape rendered at " + x + "," + y);
}


// The constructor is always the first argument
module.exports = construct(Shape, move, render);

// rect.js

var Shape = require("./shape");

// You can also just define classes by passing the named functions
// inline as arguments 

// Extend shape
var Rect = Shape.extend(
    // Named functions are great for debugging
    function Rect(x, y, width, height) {
        // Calling a parent's constructor
        Shape.init(this, x, y);
        this.w = width;
        this.h = height;
    },

    function render() {
        // Calling a parent's method
        Rect.parent.render.call(this);
        console.log("rect rendered " + this.w + " wide " +
                    "and " + this.h + " tall");
    }
);

var shape = Shape(10, 10);
var rect = Rect(5, 5, 50, 50);

console.log("\nShape?", rect.isinstance(Shape)); // -> true

// Note how the constructor is kept properly in tact, this is
// extremely helpful for debugging (you get back an object literally
// made with your constructor function)
console.log("\nType:", rect.constructor.name); // -> "Rect"