set( x, y, z, w ) {

		this._x = x;
		this._y = y;
		this._z = z;
		this._w = w;

		this._onChangeCallback();

		return this;

	}
Sets the quaternion components.

@param {number} x - The x value of this quaternion.
@param {number} y - The y value of this quaternion.
@param {number} z - The z value of this quaternion.
@param {number} w - The w value of this quaternion.
@return {Quaternion} A reference to this quaternion.