Typescript global variables

This is a contrived example, but rather than trying to push to global scope, you can use the module scope to enclose a variable that will be used from several classes.

module MyModule {
    var x: number = 5;

    export class FirstClass {
        doSomething() {
            x = 10;
        }
    }

    export class SecondClass {
        showSomething() {
            alert(x.toString());
        }
    }
}

var a = new MyModule.FirstClass();
a.doSomething();

var b = new MyModule.SecondClass();
b.showSomething();

All the usual rules about multiple things using the same variable apply here - you don't want to enforce a particular order of events on the calling code.

---

Compiles to:

var MyModule;
(function (MyModule) {
    var x = 5;

    var FirstClass = (function () {
        function FirstClass() {
        }
        FirstClass.prototype.doSomething = function () {
            x = 10;
        };
        return FirstClass;
    })();
    MyModule.FirstClass = FirstClass;

    var SecondClass = (function () {
        function SecondClass() {
        }
        SecondClass.prototype.showSomething = function () {
            alert(x.toString());
        };
        return SecondClass;
    })();
    MyModule.SecondClass = SecondClass;
})(MyModule || (MyModule = {}));

var a = new MyModule.FirstClass();
a.doSomething();

var b = new MyModule.SecondClass();
b.showSomething();

You need to define those properties as static, then you can access it easily like this,

export class Game {
    static canvas: JQuery;
    static CANVAS_WIDTH: number;
    static CANVAS_HEIGHT: number;
    bullet: Bullet;

    constructor(canvasElem: JQuery) {
        Game.canvas = canvasElem;
        Game.CANVAS_WIDTH = Game.canvas.width();
        Game.CANVAS_HEIGHT = Game.canvas.height();
    }
}

export class Bullet {
    x: number = 22;
    y: number = 22;

    public inBounds() {
        // accessing static properties
        return this.x >= 0 && this.x <= Game.CANVAS_WIDTH && this.y >= 0 && this.y <= Game.CANVAS_HEIGHT;
    }
}

---

This compiles to:

define(["require", "exports"], function(require, exports) {
    var Game = (function () {
        function Game(canvasElem) {
            Game.canvas = canvasElem;
            Game.CANVAS_WIDTH = Game.canvas.width();
            Game.CANVAS_HEIGHT = Game.canvas.height();
        }
        return Game;
    })();
    exports.Game = Game;

    var Bullet = (function () {
        function Bullet() {
            this.x = 22;
            this.y = 22;
        }
        Bullet.prototype.inBounds = function () {
            // accessing static properties
            return this.x >= 0 && this.x <= Game.CANVAS_WIDTH && this.y >= 0 && this.y <= Game.CANVAS_HEIGHT;
        };
        return Bullet;
    })();
    exports.Bullet = Bullet;
});
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