Roll20.net Script to change images on a multi-sided token

TokenRoller

/*
TokenRoller
a Roll20 API Script by Tsolval

Change, increment or decrement sides on selected rollable tokens.

Command - Action
!rt+ - Switch to the next side (increment)
!rt- - Switch to the previous side (decrement)
!rt* - Switch to a random side (randomize)
!rt# - Choose a specific side with, where # is the image index.  Remember 
        that indexes start at 0.
*/

var TokenSwitch = TokenSwitch || (function() {
    'use strict';
    
    var parseMessage = function(msg) {
        if (msg.type == "api" && msg.content.match(/^!rt[0-9*+\-]/)) {
            if (msg.selected === undefined) {
                report("You must select at least one token.");
            } else {
                let fs = msg.content.charAt(3);
                msg.selected.forEach(function(entry) {
                    if (entry._type === 'graphic') {
                        var obj = getObj(entry._type, entry._id);
                        if ('+' === fs) {
                            increment(obj);
                        } else if ('-' === fs) {
                            decrement(obj);
                        } else if ('*' === fs) {
                            randomize(obj);
                        } else if (fs.match(/[0-9]/)) {
                            change(obj, fs);
                        }
                    }
                });
            }
        }
    },
    getCleanImgSrc = function(imgsrc) {
        var parts = imgsrc.match(/(.*\/images\/.*)(thumb|med|original|max)([^?]*)(\?[^?]+)?$/);
        if(parts) {
            return parts[1]+'thumb'+parts[3]+(parts[4]?parts[4]:`?${Math.round(Math.random()*9999999)}`);
        }
        return;
    }, 
    increment = function(token) {
        let allSides = token.get('sides').split('|');
        let currSide = token.get('currentSide');
        let nextSide = (currSide + 1) % allSides.length;
        token.set({
            currentSide: nextSide,
            imgsrc: getCleanImgSrc(decodeURIComponent(allSides[nextSide]))
        });
    },
    decrement = function(token) {
        let allSides = token.get('sides').split('|');
        let currSide = token.get('currentSide');
        let prevSide = (currSide + allSides.length - 1) % allSides.length;
        token.set({
            currentSide: prevSide,
            imgsrc: getCleanImgSrc(decodeURIComponent(allSides[prevSide]))
        });
    },
    randomize = function(token) {
        let allSides = token.get('sides').split('|');
        let randSide = (randomInt(allSides.length))
        token.set({
            currentSide: randSide,
            imgsrc: getCleanImgSrc(decodeURIComponent(allSides[randSide]))
        });
    },
    change = function(token, side) {
        let allSides = token.get('sides').split('|');
        let newSide = side % allSides.length;
        token.set({
            currentSide: newSide,
            imgsrc: getCleanImgSrc(decodeURIComponent(allSides[newSide]))
        });
    },
    randomInt = function(max) {
        return Math.floor(Math.random() * max);
    },
	report = function(text) {
		sendChat('TokenSwitch',`/w gm <div>${text}</div>`);
	},
    registerEventHandlers = function() {
        on('chat:message', parseMessage);
    };
    return {
        RegisterEventHandlers: registerEventHandlers,
    };
}());

on("ready",function(){
    'use strict';
    TokenSwitch.RegisterEventHandlers();
});