@algodex/algodex-sdk/lib/utils/format/floatToFixed.js

API calls for interacting with the Algorand blockchain

/*
 * Copyright (C) 2021-2022 Algodex VASP (BVI) Corp.
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/.
 */

const Big = require('big.js');

/**
 * This is a custom implementation of Number.prototype.toFixed()
 *
 * It accepts a float (string or number) and formats it for display using
 * fixed-point notation. It rounds the number to `minDigits` digits after the
 * decimal point (or more, if necessary to show a number that isn't zero).
 *
 * Returns a string representing the given number using fixed-point notation.
 *
 * The default values for `minDigits` and `maxDigits` are for rounding a price
 * in ALGOs to at least 4 decimals (but no more than 6).
 *
 * @param {Number|String} float number to format
 * @param {Number} minDigits minimum number of digits after decimal point
 * @param {Number} maxDigits maximum number of digits after decimal point
 * @return {String}
 */
function floatToFixed(float, minDigits = 4, maxDigits = 6) {
  if (typeof float === 'undefined') throw new Error('Must have a valid float');
  let numDigits;
  const absValue = new Big(float).abs().toNumber();

  // checks for fractional numbers less than zero with preceding zeros after decimal point
  if (absValue > 0 && absValue < 0.1) {
    // if number is 0.0001, fractionalStr is '0001'
    const fractionalStr = new Big(float).toFixed(maxDigits).toString().split('.')[1];

    let precedingZeros;
    for (let i = 0; i < fractionalStr.length; i++) {
      if (fractionalStr[i] !== '0') {
        precedingZeros = i;
        break;
      }
    }

    if (precedingZeros >= minDigits && precedingZeros < maxDigits) {
      numDigits = precedingZeros + 1;
    } else {
      numDigits = minDigits;
    }
  } else {
    numDigits = minDigits;
  }

  return new Big(float).toFixed(numDigits);
}

module.exports = floatToFixed;