new.js

class MapManager {
  findPath(fromX, fromY, toX, toY) {
    /**
     * With ngraph we don't have to create grid cells if they're unoccupied, so we
     * have to verify we're not running the pathfinder against non-existent nodes.
     */
    if (this.#graph.hasNode(`${toX}|${toY}`)) {
      /**
       * It's probably not necessary to generate a new pathfinder every time right
       * now, but it'll be valuable in the future when the user gains the ability
       * to change to pathfinding algo.
       */
      return aStar(this.#graph).find(
        `${fromX}|${fromY}`,
        `${toX}|${toY}`,
      )
    }

    return null
  }
}

old.js

class MapManager {
  findPath(fromX, fromY, toX, toY) {
    /**
     * Coordinates are coming from the main map grid, which may not start at
     * `0, 0` (i.e. there may be tiles placed in the negative axial space).
     * 
     * Since the pathfinding grid cannot have coordinates in the negative axial
     * space, we have to translate our coordinates for the pathfinding grid.
     */ 
    const [
      fromPFX,
      fromPFY,
    ] = this.getPFCellCoordinates(fromX, fromY)
    const [
      toPFX,
      toPFY,
    ] = this.getPFCellCoordinates(toX, toY)

    /**
     * We have to run the pathfinder on a clone of the grid, otherwise future
     * pathfinding will break.
     */
    const grid = this.#pathfindingGrid.clone()

    const path = this.#finder.findPath(
      fromPFX,
      fromPFY,
      toPFX,
      toPFY,
      grid,
    )

    /**
     * To wrap things up, we have to translate coordinates back for the main grid.
     */
    return path.map(([x, y]) => this.getCellFromPFCoordinates(x, y))
  }
}