Premiere's Time object computation (Adobe ExtendedScript compatible)

bigint_extendedscript.jsx

// for Premiere's Time object computation (Adobe ExtendedScript Compatible)
// WORKING IN PROGRESS, NOT WELL TESTED
// License: Public Domain or CC0
// Copyleft (ɔ) Retorillo

function bigint_pad(x, L) {
  // NOTE: ExtendedScript does not support String.padStart
  var y = x.split(/(?=.)/);
  while(y.length < L) y.unshift('0');
  return y.join('');
}
function bigint_add(x, y) {
  if (!/^[0-9]+$/.test(x) || !/^[0-9]+$/.test(y))
    throw new Error("must be positive number");
  var L = Math.max(x.length, y.length);
  x = bigint_pad(x, L);
  y = bigint_pad(y, L);
  var z = [];
  var inc = false; 
  for (var c = L - 1; c >= 0; c--) {
    var digit = parseInt(x[c]) + parseInt(y[c]) + (inc ? 1 : 0)
    inc = digit > 9;
    z.unshift(digit % 10);
  }
  while (z[0] === 0) z.shift();
  if (inc) z.unshift(1);
  return z.join('');
}
function bigint_less(x, y) {
  if (!/^[0-9]+$/.test(x) || !/^[0-9]+$/.test(y))
    throw new Error("must be positive number");
  if (x.length > y.length) return false;
  if (x.length < y.length) return true;
  for (var c = 0; c < x.length; c++) {
    if (parseInt(x[c]) > parseInt(y[c])) return false;
    if (parseInt(x[c]) < parseInt(y[c])) return true;
  }
  return false;
}
function bigint_delta(x, y) {
  if (!/^[0-9]+$/.test(x) || !/^[0-9]+$/.test(y))
    throw new Error("must be positive number");
  if (bigint_less(x, y)) {
    var x_swap = x;
    x = y;
    y = x_swap;
  }
  var L = Math.max(x.length, y.length);
  x = bigint_pad(x, L);
  y = bigint_pad(y, L);
  var z = [];
  var dec1 = false, dec2 = false;
  for (var c = L - 1; c >= 0; c--) {
    var xc = parseInt(x[c]);
    dec2 = false;
    if (dec1) {
      if (xc-- < 0) {
        xc += 10;
        dec2 = true;
      }
    }
    var yc = parseInt(y[c]);
    var digit = xc - yc;
    if (digit < 0) {
      dec1 = true;
      digit += 10;
    }
    else if (!dec2) dec1 = false;
    z.unshift(digit);
  }
  while (z[0] === 0) z.shift();
  return z.join('');
}

bigint_extendedscript_test.jsx

// For Node.js
function bigint_test() {
  console.log(bigint_delta('2540160000000', '25401600000000'));
  console.log(bigint_delta('2540160000000', '25401600000000') == "22861440000000");
  console.log(bigint_delta('1000000000000', '1'));
  console.log(bigint_delta('1000000000000', '1') == "999999999999");
}
bigint_test();