Formatting a number with exactly two decimals in JavaScript

Question

I have this line of code which rounds my numbers to two decimal places. But I get numbers like this: 10.8, 2.4, etc. These are not my idea of two decimal places so how I can

Answer 1

I didn't find an accurate solution for this problem, so I created my own:

function inprecise_round(value, decPlaces) {
  return Math.round(value*Math.pow(10,decPlaces))/Math.pow(10,decPlaces);
}

function precise_round(value, decPlaces){
    var val = value * Math.pow(10, decPlaces);
    var fraction = (Math.round((val-parseInt(val))*10)/10);

    //this line is for consistency with .NET Decimal.Round behavior
    // -342.055 => -342.06
    if(fraction == -0.5) fraction = -0.6;

    val = Math.round(parseInt(val) + fraction) / Math.pow(10, decPlaces);
    return val;
}

Examples:

function inprecise_round(value, decPlaces) {
  return Math.round(value * Math.pow(10, decPlaces)) / Math.pow(10, decPlaces);
}

function precise_round(value, decPlaces) {
  var val = value * Math.pow(10, decPlaces);
  var fraction = (Math.round((val - parseInt(val)) * 10) / 10);

  //this line is for consistency with .NET Decimal.Round behavior
  // -342.055 => -342.06
  if (fraction == -0.5) fraction = -0.6;

  val = Math.round(parseInt(val) + fraction) / Math.pow(10, decPlaces);
  return val;
}

// This may produce different results depending on the browser environment
console.log("342.055.toFixed(2)         :", 342.055.toFixed(2)); // 342.06 on Chrome & IE10

console.log("inprecise_round(342.055, 2):", inprecise_round(342.055, 2)); // 342.05
console.log("precise_round(342.055, 2)  :", precise_round(342.055, 2));   // 342.06
console.log("precise_round(-342.055, 2) :", precise_round(-342.055, 2));  // -342.06

console.log("inprecise_round(0.565, 2)  :", inprecise_round(0.565, 2));   // 0.56
console.log("precise_round(0.565, 2)    :", precise_round(0.565, 2));     // 0.57