Photoshop Grid Generator

grid_builder.js

var DocumentArea = function(doc) {
  this.doc = doc;
};

DocumentArea.prototype.bounds = function() {
  return [0, 0, this.doc.width, this.doc.height];
};

var DocumentArea = function(doc) {
  this.doc = doc;
};

DocumentArea.prototype.bounds = function() {
  return [0, 0, this.doc.width, this.doc.height];
};

BOUND_LEFT = 0;
BOUND_TOP = 1;
BOUND_RIGHT = 2;
BOUND_BOTTOM = 3;

var buildArea = function(doc) {
  try {
    doc.selection.bounds;
    return new SelectionArea(doc.selection);
  } catch(e) {
    return new DocumentArea(doc);
  }
};

if (app.documents.length > 0) {
  var doc = app.activeDocument;
  var area = buildArea(doc);

  var numberColumns = parseInt(prompt("How many columns do you need?", 12));
  var bounds = area.bounds();
  var width = bounds[BOUND_RIGHT] - bounds[BOUND_LEFT];
  var columnWidth = width / numberColumns;
  var left = bounds[BOUND_LEFT];

  for(var i = 1; i < numberColumns; i++) {
    doc.guides.add(Direction.VERTICAL, i * columnWidth + left);
  }
}