operations

defines an object with custom operations

object operations;

webix.ui({
  view: "pivot",
  operations: {
    floor: v => v.reduce((acc, a) => acc + Math.floor(a), 0),
  },
  // config
});

Details

An operation can be defined as an object:

operations: {
    multiply: {
        handler: (a, b) => a * b,
        fields: 2,
        hidden: true,
        branchMode: "raw"
    }
}

handler - a function itself.
fields - optional, a number of fields to which the function should be applied. If it is not specified, its value is the number of function arguments.
branchMode - optional, a way how the aggregated data will be calculated. Possible options are "raw" - calculation is based on the raw data, and "result" - calculation is based on already calculated parent node values. If it is not specified, its value is set to "raw".
hidden - optional, if true, hides the operation from the list of operations.

If a custom function takes more than two parameters, you should use the complex function to apply it:

operations: {
    multiply: (a, b, c) => a*b*c,
},

When defining a new operation make sure to provide a corresponding label for it in locales.

// localized label for new operation
pivot.locales.en = {
  floor: "floor",
};