Iterators

Iterators offer a concise and expressive way to traverse a quadrille, especially when combined with filters. Both for...of and visit rely on the lazy cells() generator to yield filtered cells, enabling functional-style iteration without the verbosity and pitfalls of manual indexing.

Filter functions can access the { row, col, value } cell data, allowing you to express complex cell selections in a single inline predicate.

Manual Iteration Using Nested Loops

The classic approach to traversing a grid—often seen with 2D arrays or matrices—involves nested for loops:

function callback(row, col) {
  /* callback body */
}

for (let row = 0; row < quadrille.height; row++) {
  for (let col = 0; col < quadrille.width; col++) {
    callback(row, col);
  }
}

While straightforward and likely familiar, this pattern is prone to off-by-one and indexing errors, and doesn’t support filtering without additional logic. It’s a good fallback—but modern alternatives are often cleaner and safer.

⚠️

For quick prototypes or direct indexing, manual loops are still fine. But for filtering, clarity, and maintainability, use the iterator methods introduced here.

Method Overview

for...of: modern, efficient, and expressive. Supports full control flow (break, continue, etc.).
visit(callback, filter?): syntactic sugar for for...of, perfect for inline arrow functions. Also supports full cell predicates.
cells(filter?): generator used by both methods for yielding filtered cells. Use directly when chaining with methods like map, reduce, or Array.from.