Roll20 Wiki

Main Article: Sheet Worker Scripts

Auto-calculating Attributes

Example 1

Your best bet would be to avoid the autocalc fields entirely if you can. Monitor the two other fields and when they change, have a sheetworker that adds them up to the new value. Then you can refer to the new value in other calculations much easier.

on("sheet:opened change:stat_a change:stat_b", function() {
    getAttrs(["stat_a", "stat_b"], function(values) {
        setAttrs({
            "foo_modchars": parseInt(values["stat_a"]) || 0 + parseInt(values["stat_b"]) || 0
        });
    });
});

Example 2

(credit: GiGs)

I remember seeing a script someone wrote to allow you to use autocalc fields within sheet workers, but it's just simpler to use Rabulias's approach(see example 1 above).

Add the relevant stats to the on(change:) line, and duplicate the calculation within the sheet worker.

I generally don't put my working in the setattrs call, but before it so i can more easily check it. Something like

on("sheet:opened change:stat_a change:stat_b", function() {
  getAttrs(["stat_a", "stat_b"], function(values) {
      var stat_a = parseInt(values["stat_a"])||0;
      var stat_b = parseInt(values["stat_b"])||0;
      var output = stat_a + stat_b;
      setAttrs({
        "foo_modchars": output
      });
  });
});

Helper Functions

This section is for useful functions that aren't complete sheet workers, but are useful to use in sheet workers.

Function: parseValues

(credit: GiGs) Many sheet workers have a bunch of lines like this:

      var stat_a = parseInt(values["stat_a"])||0;
      var stat_b = parseInt(values["stat_b"])||0;

You might also have lines like this:

setAttrs({
   "foo_modchars": parseInt(values["stat_a"],10) || 0 + parseInt(values["stat_b"],10) || 0
});

It gets tedious typing out all that. With the function below, you would instead write them as:

var stat_a = parseValues(values,"stat_a");
var stat_b = parseValues(values,"stat_b");
setAttrs({
   "foo_modchars": parseValues(values,"stat_a") + parseValues(values,"stat_b")
});

I think that's a lot easier to read. Here's the function:

parseValues

Place this at the start of your script block, and you'll be able to use it in all your sheet workers.

const parseValues = (values, stat, type='int') => {
     if(type === 'int') return parseInt(values[stat])||0;
     else if(type === 'float') return parseFloat(values[stat])||0;
     else if(type === 'str') return values[stat];
};

By default, it returns an integer. If you call it with a second parameter, it will return either a float or a string:

parseValues(values, stat) or parseValues(values, stat, 'int') - returns an integer.
parseValues(values, stat,'float') - returns a Float (a number that is not an integer)
parseValues(values, stat, 'str') - returns the value as text. (Not really needed!)

This function does handle variable attribute names. If you were in a loop and creating attributes like, "stat" + i it will work fine.

Reuse of fields for listeners

(credit: Marco G.)

In order to prevent typing the same thing over and over again you can store the fields that you want to use in an array and reuse it for event listeners and getAttrs.

It will looks like this:

      let fields = ["str", "dex", "con"];
      on(fields.map(field => "change:" + field).join(" "), () => {
        getAttrs(fields, (values ) => {
          ....
        });
      });