Generating tables of arbitrary length.

demo.js

/* Mesh boilerplate - do not change. 2018-06-16-1 */
'use strict';

var _defProp = Object.defineProperty, _OUTPUT = {};
function _isFn(value) {return typeof value === 'function'};
function _defCell(k, c) {
    return _defProp(self, k, {configurable: true, get() {
        if (k in _OUTPUT) return _OUTPUT[k].v;
        var o = _OUTPUT[k] = {};
        var t = o.t = c.t; o.s = c.s; o.n = c.n;
        var v = c.v; v = _isFn(v)? (t? _makeTable(v()) : v()) : v;
        var f = c.f; o.f = (f) ? c.f(v) : String(v);
        var l = c.l; o.l = _isFn(l) ? l() : l;
        o.v = v; return v;
    }})
};
function _makeTable(s) {
    var t = [], cols = [], MAX = Math.max;
    for (var h in s) {
        if (h != 'length') cols.push([h,s[h].values,s[h].default])
    };
    t.length = (s.length === undefined)
        ? cols.reduce(function(a,e){return MAX(a,e[1].length)},0)
        : s.length;
    for (var i = 0, length = t.length, r; i < length; i++) {
        t[i] = r = {};
        cols.forEach(function(col) {
            var h = col[0], c = col[1][i], s = r, j = i;
            if (c === undefined) c = col[2];
            _defProp(r, h, {get: function() {
                delete this[h];
                return this[h] = (_isFn(c)) ? c.call(t, s, j) : c
            }, enumerable: true, configurable: true});
        })
    };
    return t;
};
function _calcTable(t){for(var i in t){var r=t[i];for(var h in r)r[h]}};

self.onmessage = function(e) {
    for (var k in _CELLS) _defCell(k, _CELLS[k]);
    for (var k in _CELLS) var v = self[k]; if (_CELLS[k].t) _calcTable(v);
    postMessage(_OUTPUT);
};

// Cell props: v = value or formula (fn), l = grid coordinates,
// f = format fn, s = transpose?, t = is table?, n = show name?
/* END Mesh boilerplate */

var curr_format = new Intl.NumberFormat('en-AU', { style: 'currency', currency: 'AUD' }).format
var _CELLS = {
    
    "term": {v: 5, l: [1,1], f: function(v) {return v + " years"}, s: null, n: null, t: null},
    
    "rate": {v: 0.10, l: [3,1], f: function(v) {return v * 100 + "%"}, s: null, n: null, t: null},
  
    "startBalance": {v: 200000, l: [2,1], f: curr_format, s: null, n: null, t: null},
  
    "payment": {v: function() {return startBalance * rate * Math.pow(1 + rate, term) / (Math.pow(1 + rate, term) - 1)}, 
                l: [4,1], f: curr_format, s: null, n: null, t: null},
  
    "cashflows": {
      v: function() {return {
        length: term,
        start_balance: {
          default: function(row, i) {return i === 0 ? startBalance : this[i - 1].end_balance},
          values: []
        },
        interest: {
          default: function(row, i) {return row.start_balance * rate},
          values: []
        },
        payment: {
          default: function(row, i) {return payment},
          values: []
        },
        end_balance: {
          default: function(row, i) {return row.start_balance + row.interest - row.payment},
          values: []
        },
      }}, l: [1,4], f: function(v) {
        return v.map(function(r) {
          return {
            start_balance: curr_format(r.start_balance),
            interest: curr_format(r.interest),
            payment: curr_format(r.payment),
            end_balance: curr_format(r.end_balance),
          }
        })
      }, s: null, n: null, t: true},
};