How do you round to 1 decimal place in Javascript?

Question

Can you round a number in javascript to 1 character after the decimal point (properly rounded)?

I tried the *10, round, /10 but it leaves two decimals at the end of

Answer 1

If you use Math.round(5.01) you will get 5 instead of 5.0.

If you use toFixed you run into rounding issues.

If you want the best of both worlds combine the two:

(Math.round(5.01 * 10) / 10).toFixed(1)

You might want to create a function for this:

function roundedToFixed(_float, _digits){
  var rounded = Math.pow(10, _digits);
  return (Math.round(_float * rounded) / rounded).toFixed(_digits);
}

Answer 2

Try with this:

var original=28.453

// 1.- round "original" to two decimals
var result = Math.round (original * 100) / 100  //returns 28.45

// 2.- round "original" to 1 decimal
var result = Math.round (original * 10) / 10  //returns 28.5

// 3.- round 8.111111 to 3 decimals
var result = Math.round (8.111111 * 1000) / 1000  //returns 8.111

less complicated and easier to implement...

with this, you can create a function to do:

function RoundAndFix (n, d) {
    var m = Math.pow (10, d);
    return Math.round (n * m) / m;
}

function RoundAndFix (n, d) {
    var m = Math.pow (10, d);
    return Math.round (n * m) / m;
}
console.log (RoundAndFix(8.111111, 3));

EDIT: see this How to round using ROUND HALF UP. Rounding mode that most of us were taught in grade school

Answer 3

Why not just

let myNumber = 213.27321;
+myNumber.toFixed(1); // => 213.3

1. toFixed: returns a string representing the given number using fixed-point notation.
2. Unary plus (+): The unary plus operator precedes its operand and evaluates to its operand but attempts to convert it into a number, if it isn't already.

Answer 4

If your method does not work, plz post your code.

However,you could accomplish the rounding off task as:

var value = Math.round(234.567*100)/100

Will give you 234.56

Similarly

 var value = Math.round(234.567*10)/10

Will give 234.5

In this way you can use a variable in the place of the constant as used above.

Answer 5

var num = 34.7654;

num = Math.round(num * 10) / 10;

console.log(num); // Logs: 34.8

Answer 6

I found a way to avoid the precision problems:

function badRound (num, precision) {
    const x = 10 ** precision;
    return Math.round(num * x) / x
}
// badRound(1.005, 2) --> 1

function round (num, precision) {
    const x = 10 ** (precision + 1);
    const y = 10 ** precision;
    return Math.round(Math.round(num * x) / 10) / y
}
// round(1.005, 2) --> 1.01