A mob damage calculator for DND 5th edition on Roll20.

AutoMob5e.js

/*
 AutoMob5e.js by Spencer Moran. MIT License
 
 This program automatically calculates mob combat attacks
 and damage based on a few input values, complete with a
 handy query macro to speed things along. You can modify the
 generated macro if you want to save time with some default 
 values.
 Intended for use with DND 5e.
 
 Commands:
 1. !automob <ac> <attack bonus> <creature count> <avg damage> <multiattack>
   Example: !automob 14 5 8 4 2
 2. !automob_getmacro
 3. !autoMob_help
*/


on('chat:message', function(msg){
    "use strict";
    
    if('api' !== msg.type) {
        return;
    }

    var args = msg.content.split(/\s+/);
    
    if (args[0] == '!automob')
    {
        let ac = parseInt(args[1]);
        let attackBonus = parseInt(args[2]);
        let creaturesNeeded = automob_getReqCreatures(ac-attackBonus);
        let numCreatures = parseInt(args[3]);
        let numHits = Math.floor(parseInt(args[3])/creaturesNeeded);
        let avgDam = parseInt(args[4]);
        let atkNum = parseInt(args[5]);
        let atkDam = parseInt(args[4]) * parseInt(args[5]);
        let totalDam = atkDam * numHits;
        sendChat("AutoMob5e",'&{template:default} {{name=Mob Attack}} {{Target AC='+ac+'}}{{Attack bonus='+attackBonus+'}}{{Creatures needed for 1 hit='+creaturesNeeded+'}}{{Number of creatures='+numCreatures+'}}{{Number of creatures that hit='+numHits+'}}{{Avg damage per hit='+avgDam+'}}{{Number of attacks per creature='+atkNum+'}}{{Attack damage per creature hit='+atkDam+'}}{{Total damage from all hits='+totalDam+'}}');
        
    } else if (args[0] == '!automob_getmacro'){
        automob_getMacro(msg.playerid);
    } else if (args[0] == '!automob_help'){
        sendChat("AutoMob5e", '&{template:default} {{name=AutoMob Commands}} {{ !automob (ac) (atkBonus) (creatures) (avgDamage) (atkCount) }} {{ !automob_getmacro }}')
    } else{
        return;
    }
});

function automob_getReqCreatures(num){
    if(num <= 5){
        return 1;
    }
    else if (num <= 12){
        return 2;
    }
    else if (num <= 14){
        return 3;
    }
    else if (num <= 16){
        return 4;
    }
    else if (num <= 18){
        return 5;
    }
    else if (num == 19){
        return 10;
    }else{
        return 20;
    }
}

function automob_getMacro(id){
    createObj('macro', {
        _playerid: id,
        name: "Query-Mob-Attack",
        action: "!automob ?{Target AC|} ?{Attack Bonus|} ?{Number of Attackers|} ?{Average Damage of One Hit|} ?{Number of attacks|}",
        visibleto: 'all',
        istokenaction: false
    });
    sendChat("AutoMob", "Macro added. Look for 'Query-Mob-Attack' in the macro tab");
}