The toMatrix() method of the CSSTransformComponent interface returns a DOMMatrix object.
All transform functions can be represented mathematically as a 4x4 transformation matrix. This is explained in detail in Understanding the CSS Transforms matrix.
Note: The is2D property affects what transform, and therefore type of matrix that will be returned. CSS 2D and 3D transforms are different for legacy reasons. A brief explanation of 2D vs. 3D transforms can be found in Using CSS transforms.