Format number for only 2 digits

Question

I have a script that returns: 4.499999999999

But I wanted it to return only 4.4 or round to 4.5, just do not want it to stay more than 1 digit after the comma, how to do?

Answer 1

To round to the nearest number, the simplest is to use toFixed:

var x = 4.499999999999999;
var y = x.toFixed(1);

document.querySelector("body").innerHTML += "<p>" + y + "</p>";

Already to round down, it is necessary to use the function floor and some other calculation:

var x = 4.499999999999999;
var y = Math.floor(10*x)/10;

document.querySelector("body").innerHTML += "<p>" + y + "</p>";

Note that the first method converts the number to a string, while the second only performs a calculation with it (the result remains a number). I can’t think of an example, but it is possible that even after the calculation the number is not as accurate as you want (given the limitations of the floating point representation) - so it is advisable to use toFixed also in the result, if you use method 2.

Answer 2

If the number is in format string and you want to round off to string you have two possibilities:

1 - keep string and simply cut the size after stitch (floor)

var n = '4.499999999999999'.split('.') ;
n = [n[0], n[1][0]].join('.');                          // '4.4'

2 - round to 4.5 in the case of your example

var n = parseFloat('4.499999999999999', 10).toFixed(1); // '4.5'

If the number is in format number and you want to round off to number you have three possibilities:

1 - round (round to nearest house)

var n = Math.round(4.499999999999999 * 100) / 100;      // 4.5

2 - Ceil (round to the top)

Math.ceil(4.499999999999999 * 10) / 10;                 // 4.5

3 - floor (round down)

var n = Math.floor(4.499999999999999 * 10) / 10;        // 4.4