Roll20 Wiki

One request that crops up on the roll20 forums over and over again, is how can you add up all the items in a repeating section?

Say you have an inventory section, listing the items you are carrying, and you need their total weight. Or you have section listing all the coins of different types, and you want their values. Or a skill or power section, and you want the total character points used to buy them.

The sheet worker function below will do that for you. Some examples of how to use it are listed below.

repeatingSum Function

Include the following function - without changes - in the sheet worker script section of your character sheet.

/* ===== PARAMETERS ==========
destinations = the name of the attribute that stores the total quantity
        can be a single attribute, or an array: ['total_cost', 'total_weight']
        If more than one, the matching fields must be in the same order. 
    section = name of repeating fieldset, without the repeating_
    fields = the name of the attribute field to be summed
          destination and fields both can be a single attribute: 'weight'
          or an array of attributes: ['weight','number','equipped']
*/
const repeatingSum = (destinations, section, fields) => {
    if (!Array.isArray(destinations)) destinations = [destinations.split(',')];
    if (!Array.isArray(fields)) fields = [fields];
    getSectionIDs(`repeating_${section}`, idArray => {
        const attrArray = idArray.reduce((m, id) => [...m, ...(fields.map(field => `repeating_${section}_${id}_${field}`))], []);
        getAttrs([...attrArray], v => {
            const getValue = (section, id, field) => v[`repeating_${section}_${id}_${field}`] === 'on' ? 1 : parseFloat(v[`repeating_${section}_${id}_${field}`]) || 0;
            const commonMultipliers = (fields.length <= destinations.length) ? [] : fields.splice(destinations.length, fields.length - destinations.length);
            const output = {};
            destinations.forEach((destination, index) => {
                output[destination] = idArray.reduce((total, id) => total + getValue(section, id, fields[index]) * commonMultipliers.reduce((subtotal, mult) => subtotal * getValue(section, id, mult), 1), 0);
            });
            setAttrs(output);
        }); 
    }); 
};

Using The Function

Simple Example

Let's say you have an fieldset called repeating_inventory, and in that set you have fields item_name and item_weight. You want to sum all the weights, and show that in an attribute outside the fieldset named encumbrance_total.

You'd add the above function, and the following worker:

on('change:repeating_inventory remove:repeating_inventory', function() {
	repeatingSum("encumbrance_total","inventory","item_weight");
});

Weight * Number

Most inventory lists are a little more complicated. You might have an extra field named item_number. For instance, your equipment list might include:

item_name: bow, item_weight: 3, item_number: 1
item_name: arrows: item_weight: 0.1, item_number: 20

and so on. In this case, you'd use the following function:

on('change:repeating_inventory remove:repeating_inventory', function() {
	repeatingSum("encumbrance_total","inventory",["item_weight","item_number"]);
});

When using multiple inputs multiplied together, set them up as an array of attribute names, like: ['weight','number'], instead of 'weight'.

Conditional Sums (e.g. using a Checkbox)

You could use it for conditional items. Let's say you have a repeating_armour fieldset, with field names, armour_piece and armour_worn. Armour_worn is a checkbox. So, you can list a variety of armours, and decide which ones you are wearing by ticking the checkbox. The following function would total the worn armour pieces and add it to an armour_weight attribute, and ignore the armour not being worn.

on('change:repeating_armour remove:repeating_armour', function() {
	repeatingSum("armour_weight", "armour",["armour_piece","armour_worn"]);
});

Note: this works because the a checked Checkbox has a default value of 'on' when checked, and '0' when unchecked. This script treats any text value as a number value of 1, so even if you don't set a value for the checkbox in the html, this will work.

Multiplying the Total

For a final example, lets say you have a repeating_coinage fieldset, with fields coin_name, coin_value, and coin_number. In this set, names and values are fixed (copper, 1, silver, 10, gold, 100), and players enter the number of each they have. You want to report (a) the total value, and (b) the total weight of the coins.

on('change:repeating_coinage remove:repeating_coinage', function() {
	repeatingSum("total_coin_value", "coinage", ["coin_number", "coin_value"]);
	repeatingSum("total_coin_weight", "coinage", ["coin_number", "coin_weight"], '0.02');
});

The first repeatingSum above multiples the number gold coins by gold value, adds that to the number of silver coins multiplied by silver value, and adds to that the number of copper coins multiplied by copper value. The second repeatingSum does the same for weights, but then multiples the total weight by 0.02 (so you get 50 coins per pound). This allows you to list coin weights as relative weights - lets say copper and silver coins both weigh then same, so the coin_weight is 1 for those. But gold coins are heavier and have a coin_weight of 2.

Author: GiGs(G-G-G on github), with help from The Aaron, inspired by a script created by Finderski.

Related Pages

Sheetworker Examples for Non-programmers
Sheetworker Snippets - short, practical examples of sheetworker use
Universal Sheet Workers - How to create one function that can handle a bunch of similar sheet workers