A script for the roll20 api to pick a random encounter.

Roll20 Random Encounters

// A shorthand to create new events in the encounters table.
var event = function(freq, msg) {
    return {message: msg, frequency: freq};
};
            

// The encounter table. Create a new section and populate it with events. The
// event text will be displayed in the GM chat window if it is selected.
// Events with a frequency of '3' will happen 3 times as often as events with
// a frequency of '1'. 
var encounters = {
  forest: [
    event(1, "[[5d20]] dragons swoop down from the sky"),
    event(2, "[[1d4]] goblins scouts are hidden in a bush"),
    event(3, "a [[3d9]] large goblin hunty party is returning (injured) from a hunt"),
    event(2, "A meteor crashes down next to the players"),
    event(1, "everyone dies.")
    ],
  desert: [
    event(100, "A plain cactus blocks your path."),
    event(1, "You find drinkable water."),
  ]
};

// A shorthand to whisper stuff to the GM>
var say = function(msg) {
    sendChat("Table", "/w gm " + msg);
}

// Pick a random event from an array of events, respecting the weights
// of the events.
var resolve = function(table) {
    var total = 0;
    for (i in table) {
        total += table[i].frequency;
    };
    var roll = randomInteger(total);
    log("total is " + total + " roll " + roll);
    for (i in table) {
        roll -= table[i].frequency;
        if (roll <= 0) {
            return table[i].message;
        }
    }
    return "something bad happened";
};
      
on("chat:message", function(msg) {
    if (msg.type != "api" || msg.content.indexOf("!enc-") !== 0) {
        return;
    }
    
    var loc = msg.content.replace("!enc-", "");
    if (!(loc in encounters)) {
        var choices = []
        for (var c in encounters) {
            choices.push("!enc-" + c);
        }
        say("Couldn't find " + loc + ". Try: " + choices);
        return;
    }
    var result = resolve(encounters[loc]);
    say("Rolling for " + loc.toUpperCase() + " random encounter: [[1d20]]. Found: " + result);
});