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I'm getting this formula, represented in values:

value = 0.0343 + (9 * 1.45/1000);

This gives this result: 0.047349999999999996

If I try to round it to 4 characters, it whould be 0.0474, but the nearest I can get in javascript is 0.0473

Searching for solutions on the web, I've found nothing that helps. These are some possible solutions I found:

value = Math.round(value * 100000) / 100000;   // still gives 0.0473

This function, which still gives 0.0473: 

function round (value, decimals) {
    return Number(Math.round(value+'e'+decimals)+'e-'+decimals);
};

Or the solution presented here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/round

// Closure
(function() {
  /**
   * Decimal adjustment of a number.
   *
   * @param {String}  type  The type of adjustment.
   * @param {Number}  value The number.
   * @param {Integer} exp   The exponent (the 10 logarithm of the adjustment base).
   * @returns {Number} The adjusted value.
   */
  function decimalAdjust(type, value, exp) {
    // If the exp is undefined or zero...
    if (typeof exp === 'undefined' || +exp === 0) {
      return Math[type](value);
    }
    value = +value;
    exp = +exp;
    // If the value is not a number or the exp is not an integer...
    if (isNaN(value) || !(typeof exp === 'number' && exp % 1 === 0)) {
      return NaN;
    }
    // Shift
    value = value.toString().split('e');
    value = Math[type](+(value[0] + 'e' + (value[1] ? (+value[1] - exp) : -exp)));
    // Shift back
    value = value.toString().split('e');
    return +(value[0] + 'e' + (value[1] ? (+value[1] + exp) : exp));
  }

  // Decimal round
  if (!Math.round10) {
    Math.round10 = function(value, exp) {
      return decimalAdjust('round', value, exp);
    };
  }
  // Decimal floor
  if (!Math.floor10) {
    Math.floor10 = function(value, exp) {
      return decimalAdjust('floor', value, exp);
    };
  }
  // Decimal ceil
  if (!Math.ceil10) {
    Math.ceil10 = function(value, exp) {
      return decimalAdjust('ceil', value, exp);
    };
  }
})();

which gives 0, if I call:

Math.round10(value, 1);

Any other suggestion?

luis.ap.uyen
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    [What Every Computer Scientist Should Know About Floating-Point Arithmetic](https://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html) – Adriano Repetti May 02 '16 at 12:11
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    Here is the code from the duplicate you might want to use: `function strip(number) { return (parseFloat(number.toPrecision(12))); } var value = 0.0343 + (9 * 1.45/1000); /*This gives this result: 0.047349999999999996 */ var rounded = strip(value).toFixed(4)` – mplungjan May 02 '16 at 12:25
  • @mplungjan: Your suggestion gives this result in my browser: 0.04765, but this is already an approach to achieve the correct result because it's easy to round once I get this number. I'm going to add it as a possible solution. – luis.ap.uyen May 02 '16 at 13:20
  • Well, since this question has been closed, the function I'm using here: `function round (value, precision) { return parseFloat((parseFloat(value.toPrecision(precision)).toFixed(precision))); };` – luis.ap.uyen May 02 '16 at 13:23
  • That is not likely working the way you would expect. The toPrecision and toFixed are not working the same way. You likely want toPrecision(12) and toFixed(4) – mplungjan May 02 '16 at 13:43

0 Answers0