toFloat64Array

The toFloat64Array() method of the DOMMatrixReadOnly interface returns a new Float64Array containing all 16 elements (m11, m12, m13, m14, m21, m22, m23, m24, m31, m32, m33, m34, m41, m42, m43, m44) which comprise the matrix. The elements are stored into the array as double-precision floating-point numbers in column-major (colexographical access, or "colex") order. (In other words, down the first column from top to bottom, then the second column, and so forth.)

MDN Reference