Typescript Either

gistfile1.js

interface Either {
	isRight: Boolean;
	isLeft: Boolean;
	left: LeftProjection;
	right: RightProjection;
}

class Right implements Either {
	isRight: Boolean = true;
	isLeft: Boolean = false;
	right: RightProjection;
	left: LeftProjection;
	constructor(a: any) {
		this.right = new RightProjection(this, a)
		this.left = new LeftProjection(this, a)
	}
}

class Left implements Either {
	isRight: Boolean = false;
	isLeft: Boolean = true;
	right: RightProjection;
	left: LeftProjection;
	constructor(a: any) {
		this.right = new RightProjection(this, a)
		this.left = new LeftProjection(this, a)
	}
}

class RightProjection {
	private a: any;
	private e: Right;
	constructor(e: Right, a: any) {
		this.a = a
		this.e = e
	}
	fmap (f: (any) => any): Right {
		if (this.e.isRight) {
			return new Right(f(this.a))	
		} else {
			return this.e
		}
	}
	bind (f: (any) => Either): Either {
		if (this.e.isRight) {
			return f(this.a)
		} else {
			return this.e
		}
	}
}

class LeftProjection {
	private a: any;
	private e: Left;
	constructor(e: Left, a: any) {
		this.a = a
		this.e = e
	}
	fmap (f: (any) => any): Left {
		if (this.e.isLeft) {
			return new Left(f(this.a))	
		} else {
			return this.e
		}
	}
	bind (f: (any) => Either): Either {
		if (this.e.isLeft) {
			return f(this.a)
		} else {
			return this.e
		}
	}
}