Matrix Math for Developers Who Skipped Linear Algebra

If you work with graphics, machine learning, game development, or 3D rendering, you need matrix operations. If you skipped linear algebra in college (or never took it), here is the practical subset that covers most real-world use cases. What a matrix is A matrix is a 2D array of numbers. That is all. No mystery. A 3x3 matrix has 3 rows and 3 columns: | 1 2 3 | | 4 5 6 | | 7 8 9 | In JavaScript: const matrix = [ [ 1 , 2 , 3 ], [ 4 , 5 , 6 ], [ 7 , 8 , 9 ] ]; Matrix addition and subtraction Element-wise. Both matrices must have the same dimensions. function add ( A , B ) { return A . map (( row , i ) => row . map (( val , j ) => val + B [ i ][ j ])); } Matrix multiplication This is where most developers stumble. Matrix multiplication is NOT element-wise. The element at position (i,j) in the result is the dot product of row i from matrix A and column j from matrix B. Requirements: A must have the same number of columns as B has rows. An m*n matrix times an n*p matrix produces an m*p matri