Objects with self-referencing getters can be used like functions in JavaScript. Because Mesh spreadsheets are just objects, we can use this to turn spreadsheets into functions.

use_spreadsheet_as_function.js

// Define a sheet (ATTACHMENTS omitted for brevity)
const calc = {
    term: 3,
    rate: 0.05,
    start_value: 100,
    get end_value() {return this.start_value * (1 + this.rate) ** this.term}
}

// Simple example of using a sheet as a template -
// equivalent in Excel would be overwriting a cell,
// but this lets you do it programmatically within the sheet UI
const new_calc = {__proto__: calc, start_value: 200}
console.log("Simple example:", new_calc.end_value)

// Scenario analysis across arbitrary inputs - would require a data table in Excel
const scenarios = {
    terms: [1, 2, 3, 4, 5], 
    get end_values() {return this.terms.map(t => ({__proto__: calc, term: t}.end_value))}
}
console.log("Scenarios 1:", scenarios.end_values)

// Can also define the scenario analysis *within* the same sheet;
// need to be careful with use of 'this', though, if the objects get more nested
const calc_2 = {
    term: 3,
    rate: 0.05,
    start_value: 100,
    get end_value() {return this.start_value * (1 + this.rate) ** this.term},
    get scenarios() {return [1, 2, 3].map(t => ({__proto__: this, term: t}.end_value))}
    // could also use calc_2 instead of this:
    // get scenarios() {return [1, 2, 3].map(t => ({__proto__: calc_2, term: t}.end_value))}
}
console.log("Scenarios 2:", calc_2.scenarios)

// Finally, we can omit 'this' from the getter variable lookups using 'with',
// at the expense of 'use strict' compliance.
const calc_3 = {
    term: 3,
    rate: 0.05,
    start_value: 100,
    get end_value() {with (this) {return start_value * (1 + rate) ** term}},
    get scenarios() {return [1, 2, 3].map(t => ({__proto__: this, term: t}.end_value))}
}
console.log("Scenarios 3:", calc_3.scenarios)