function Point(x, y) {
this.x = x;
this.y = y;
}
function Shape() {
this.points = [];
this.init();
}
Shape.prototype = {
constructor: Shape,
init: function(){
if (this.context === undefined) {
Shape.prototype.context = document.getElementById('canvas').getContext('2d');
};
if(this.name === undefined){
Shape.prototype.name = 'generic shape'
}
},
draw: function(){
var i, ctx = this.context;
ctx.strokeStyle = 'rgb(0,0,255)';
ctx.beginPath();
ctx.moveTo(this.points[0].x, this.points[0].y);
for (i = 1; i<this.points.length; i++) {
ctx.lineTo(this.points[i].x, this.points[i].y);
}
ctx.closePath();
ctx.stroke();
},
fill: function(color){
var ctx = this.context;
ctx.fillStyle = color;
ctx.fill();
},
say_name: function(){console.log('Hello my name is '+ this.name)}
};
function Triangle(a,b,c){
this.points = [a, b, c];
this.name = 'Triangle'
this.context = document.getElementById('canvas').getContext('2d');
}
function Rectangle(side_a, side_b){
var p = new Point(200, 200);
this.points = [
p,
new Point(p.x + side_a, p.y),// top right
new Point(p.x + side_a, p.y + side_b), // bottom right
new Point(p.x, p.y + side_b)// bottom left
];
this.name = 'Rectangle'
this.context = document.getElementById('canvas').getContext('2d');
}
(function(){
var s = new Shape();
Triangle.prototype = s;
Rectangle.prototype = s;
})();
function testTriangle(){
var p1 = new Point(100, 100);
var p2 = new Point(300, 100);
var p3 = new Point(200, 0);
return new Triangle(p1, p2, p3);
}
function testRectangle(){
return new Rectangle(100, 100);
}
function make_me_crazy(){
var t = testTriangle();
t.say_name();
t.draw();
t.fill('red');
var r = testRectangle();
r.draw();
r.say_name();
}
make_me_crazy();
<canvas height='600' width='800' id='canvas'></canvas>
