How do I make it so that you walk left, everywhere you hold down A key?

I heard I should maybe use quaternions or something like that?
Apologies for not providing a playground; I wasn’t sure how to put it there as there are a lot of modules in my project

For anyone in the future who may have the same issue, i first created a seperate function which listened into keyboard presses and assigned it to some booleans. For example, if A was pressed, moveLeft would be equal to true.
Then in my movement function I applied friction then assigned the movement booleans to directions which I then normalized. I then multiplied forward/right direction, direction, speed and delta and added it to the velocity.
Do note, JS cannot do vector maths, so I used babylon.js’ built-in vector maths functions.

const keyboardMovement = (scene, engine) => {
scene.registerBeforeRender(() => {
delta = engine.getDeltaTime();
direction = new Vector3.Zero();
forwardDirection = playerCylinder.getDirection(new Vector3(0, 0, 1));
forwardDirection.normalize();
rightDirection = playerCylinder.getDirection(new Vector3(1, 0, 0));
rightDirection.normalize();
//Slows down the current movement like a friction force
velocity.x *= friction * delta;
velocity.z *= friction * delta;
//Gravity is applied
velocity.y += 9.8 * 100.0 * delta; //100.0 = mass
direction.z = Number(moveBackward) - Number(moveForward);
direction.x = Number(moveLeft) - Number(moveRight);
direction.normalize(); // gives direction a length of 1 so diagonal movement isn't faster
if (moveForward || moveBackward || moveLeft || moveRight) {
//JS can't do maths with built in operators like * or + for vectors, so we have to use their custom vector maths functions
//velocity += rightDirection * direction.x * speed * delta;
// left & right
velocity = velocity.add(
rightDirection.scale(direction.x * speed * delta)
);
//velocity += forwardDirection * direction.z * speed * delta;
// forward & back
velocity = velocity.add(
forwardDirection.scale(direction.z * speed * delta)
);
}
//Apply velocities to position
playerCylinder.position.x += -velocity.x * delta; //Left/Right
playerCylinder.position.z += -velocity.z * delta; //Forwards/Backwards
});
};