Roll20 API: LokiTrapMan -- reoganization of Loki's trap script.

LokiTrapMan.js

// GIST: https://gist.github.com/shdwjk/054574d39c166d50865c

var LokiTrapMan = LokiTrapMan || ( function() {
	'use strict';

	// Here is the bulk of where you define a trap and cusomize the events. This is an array of all traps on your campaign (I only have 1 defined).
	// Trap coordinates are defined in squares, not pixals.  A trap location is defined as a rectange having two points (x1,y1 to x2,y2)
	// Set the pageID and region of the trap and when a token enters this area the defined callback in the array will be triggered.
	var traps = [
		// In this example when a charater lands next to (or on) a placed npc he (and his campfire) disappears in a firey explosion.
		{
			pageID: "7F73B956-71C3-4C5B-8C72-576EE4F15EA4",
			xP1: 16,
			yP1: 2,
			xP2: 18,
			yP2: 4,
			fired: false,
			fireEvent: function(firedBy) {
				//Find objects I want to manipulate
				var explode = findObjs({_type: "graphic", name: "MysteryExplode"})[0],
				    man = findObjs({_type: "graphic", name: "Mystery Man"})[0],
				    campfire = findObjs({_type: "graphic", name: "MysteryCampfire"})[0],
					flashCount,
					flashObj;

				// GM emote a notification of the trap trigger and by whom.
				sendChat('', "/emas The camper laughs at "+ firedBy.get("name") +" and disappears in a firey explosion. You take 2 points of damage");

				// Hide the npc and the campfire
				man.set({
					'layer': 'gmlayer'
				});
				campfire.set({
					'layer': 'gmlayer'
				});

				// Animate a quick flashing explosion
				flashCount = 0;
				flashObj = setInterval(function(){
					var nextLayer = (explode.get("layer") === "gmlayer") ? "objects" : "gmlayer";
					explode.set({
						'layer': nextLayer
					});
					flashCount++;
					// ensure the explosion is hidden before we kill the animation.
					if (flashCount >= 20 && explode.get("layer") === "gmlayer") {
						clearInterval(flashObj);
					}
				}, 50);
			}
		}
	],

    checkTrapTrigger = function(firedBy) {
        // Get the page ID and location of the changed token
        var pageID = firedBy.get("_pageid"),
			xLoc =  Math.ceil(firedBy.get("left")/70),
			yLoc =  Math.ceil(firedBy.get("top")/70);
        
        log("Checking for trap triggers at " +pageID+":"+ xLoc + ","+yLoc);
        
        // For each defined trap check to see if the token landed on the trap.
        // Future work will have options to control triggering on crossing over and\or landing on it to trigger it
        traps.forEach(function(opts){
			log("Checking trap "+opts.pageID+":"+parseInt(opts.xP1,10)+","+parseInt(opts.yP1,10)+";"+parseInt(opts.xP2,10)+","+parseInt(opts.yP2,10),10);
            if ( !opts.fired
            && opts.pageID === pageID
            && xLoc >= parseInt(opts.xP1,10)
            && xLoc <= parseInt(opts.xP2,10)
            && yLoc >= parseInt(opts.yP1,10)
            && yLoc <= parseInt(opts.yP2,10)
            ) {
                opts.fired = 1; //Only fire a trap event once
                opts.fireEvent(firedBy); // Fire the trap callback taking some action
            }
        });
    },

	onChangeGraphic = function (obj, prev) {
        //Only token linked to a char sheet will trigger traps.
        if (obj.get("represents") !== "") {
            checkTrapTrigger(obj);
        }
    },

	registerEventHandlers = function() {
		on('change:graphic', onChangeGraphic);
	}
	;

	return {
		RegisterEventHandlers: registerEventHandlers
	};
}() );


on("ready", function() {
	'use strict';

	LokiTrapMan.RegisterEventHandlers();
});