Three.js Resizing Canvas

So the canvas element can be resized like every other element. What you want to do is tell the render and camera to resize the contents of your canvas as well.

window.addEventListener( 'resize', onWindowResize, false );

function onWindowResize(){

    camera.aspect = window.innerWidth / window.innerHeight;
    camera.updateProjectionMatrix();

    renderer.setSize( window.innerWidth, window.innerHeight );

}