Format number to always show 2 decimal places

Question

I would like to format my numbers to always display 2 decimal places, rounding where applicable.

Examples:

number     display
------     -------
1          1.00
1.341      1.34
1.345      1.35

I have been using this:

parseFloat(num).toFixed(2);

But it's displaying 1 as 1, rather than 1.00.

Answer 1

You are not giving us the whole picture.

javascript:alert(parseFloat(1).toFixed(2)) shows 1.00 in my browsers when I paste it int0 the location bar. However if you do something to it afterwards, it will revert.

var num = 2
document.getElementById('spanId').innerHTML=(parseFloat(num).toFixed(2)-1)


shows 1 and not 1.00

Answer 2

Extend Math object with precision method

Object.defineProperty(Math, 'precision',{
   value: function (value,precision,type){
             var v = parseFloat(value),
                 p = Math.max(precision,0)||0,
                 t = type||'round';
              return (Math[t](v*Math.pow(10,p))/Math.pow(10,p)).toFixed(p);
          }
    });

console.log(
    Math.precision(3.1,3), // round 3 digits 
    Math.precision(0.12345,2,'ceil'), // ceil 2 digits
    Math.precision(1.1) // integer part
)

Answer 3

A much more generic solution for rounding to N places

function roundN(num,n){
  return parseFloat(Math.round(num * Math.pow(10, n)) /Math.pow(10,n)).toFixed(n);
}


console.log(roundN(1,2))
console.log(roundN(1.34,2))
console.log(roundN(1.35,2))
console.log(roundN(1.344,2))
console.log(roundN(1.345,2))
console.log(roundN(1.344,3))
console.log(roundN(1.345,3))
console.log(roundN(1.3444,3))
console.log(roundN(1.3455,3))

Output

1.00
1.34
1.35
1.34
1.35
1.344
1.345
1.344
1.346

Answer 4

I had to decide between the parseFloat() and Number() conversions before I could make toFixed() call. Here's an example of a number formatting post-capturing user input.

HTML:

<input type="number" class="dec-number" min="0" step="0.01" />

Event handler:

$('.dec-number').on('change', function () {
     const value = $(this).val();
     $(this).val(value.toFixed(2));
});

The above code will result in TypeError exception. Note that although the html input type is "number", the user input is actually a "string" data type. However, toFixed() function may only be invoked on an object that is a Number.

My final code would look as follows:

$('.dec-number').on('change', function () {
     const value = Number($(this).val());
     $(this).val(value.toFixed(2));
});

The reason I favor to cast with Number() vs. parseFloat() is because I don't have to perform an extra validation neither for an empty input string, nor NaN value. The Number() function would automatically handle an empty string and covert it to zero.

Answer 5

(num + "").replace(/^([0-9]*)(\.[0-9]{1,2})?.*$/,"$1$2")

Answer 6

This is how I solve my problem:

parseFloat(parseFloat(floatString).toFixed(2));