MZ - I need help with UP/Down Diagonal Slopes

/*:
 * @target MZ
 * @plugindesc Patch for Cae_SlopeMove - blocked up/down moves can go up/down slopes.
 * @author Caethyril
 * @url https://forums.rpgmakerweb.com/threads/165597/
 * @base Cae_SlopeMove
 * @orderAfter Cae_SlopeMove
 * @help Free to use and/or modify for any project, no credit required.
 */

// Override - allow up/down to be slope moves as well.
CAE.SlopeMove.isSlopeMove = function(d, m) {
  return m !== 0 && d % 2 === 0;
};

// Override - get X-offset for slope move.
CAE.SlopeMove.getXMove = function(d, m) {
  switch (d) {
    case 1: case 2: case 3:
      return m > 0 ? 4 : 6;
    case 7: case 8: case 9:
      return m < 0 ? 4 : 6;
  }
  return 0;
};

// Override - rewrite because now we can receive directions 2 & 8.
CAE.SlopeMove.getYMove = function(d, m) {
  switch (d) {
    case 1: case 4: case 7:
      return m > 0 ? 2 : 8;
    case 3: case 6: case 9:
      return m < 0 ? 2 : 8;
  }
  return 0;
};

// Override - also offset target X if appropriate.
Game_CharacterBase.prototype.getSlopeNext = function(d, m) {
  const dx = this.canPass(this.x, this.y, d) ? d : CAE.SlopeMove.getXMove(d, m);
  const dy = CAE.SlopeMove.getYMove(d, m);
  return {
    x: $gameMap.roundXWithDirection(this.x, dx),
    y: $gameMap.roundYWithDirection(this.y, dy)
  };
};

/*:
 * @target MZ
 * @plugindesc Attempting to walk onto a marked tile makes you move diagonally.
 * @author Caethyril
 * @url https://forums.rpgmakerweb.com/threads/165597/
 * @help Edit the marked tile region ID and/or terrain tag in the plugin code.
 *
 * Free to use and/or modify for any project, no credit required.
 */
void (() => {
'use strict';

    /**
     * Region ID for "marked" tiles.
     * If `0`, region ID will not be checked.
     */
    const REGION_ID = 1;

    /**
     * Terrain tag for "marked" tiles.
     * If `0`, terrain tag will not be checked.
     */
    const TERRAIN_TAG = 0;

    /**
     * @param {number} x
     * Map tile coordinate X.
     * @param {number} y
     * Map tile coordinate Y.
     * @returns {boolean}
     * `true` iff map tile at given coordinates is "marked".
     */
    const isMarkedTile = function(x, y) {
        return (REGION_ID   && $gameMap.regionId(x, y)   === REGION_ID  )
            || (TERRAIN_TAG && $gameMap.terrainTag(x, y) === TERRAIN_TAG);
    };

    /**
     * @param {function} f
     * Function checking diagonal passability: `(dx, dy) => true|false`.
     * @param {number} d
     * Numpad direction of predicted arrival into marked tile.
     * @returns {[dx:number,dy:number]}
     * Valid diagonal move numpad directions (horz, vert), or `[0, 0]`.
     */
    const getDirection = function(f, d) {
        switch (d) {
            case 2: case 8:
                for (const dx of [4, 6])
                    if (f(dx, d))
                        return [dx, d];
                break;
            case 4: case 6:
                for (const dy of [2, 8])
                    if (f(d, dy))
                        return [d, dy];
                break;
        }
        return [0, 0];
    };

    // Patch - replace straight moves onto marked tiles with diagonals, where available.
    const alias = Game_Player.prototype.moveStraight;
    Game_Player.prototype.moveStraight = function(d) {
        const x = $gameMap.roundXWithDirection(this.x, d);
        const y = $gameMap.roundYWithDirection(this.y, d);
        if (isMarkedTile(x, y)) {
            const [dx, dy] = getDirection(
                this.canPassDiagonally.bind(this, this.x, this.y), d
            );
            if (dx && dy)
                this.moveDiagonally(dx, dy);
        } else
            alias.apply(this, arguments);
    };

})();