Javascript always round up to X decimal places

Question

I need to write a function that will ALWAYS round up, but will either round up to 0, 1 or 2 decimal places, depending on if the function is passed a 0, 1 or 2.

Examples...

Round to 0 decimal places: 13.4178 = 14

Round to 1 decimal place: 13.4178 = 13.5

Round to 2 decimal places: 13.4178 = 13.42

I've found Math.ceil but this only rounds up to a whole integer and to fixed() will round up or down, not just up. Is there a way to round up in the way I've described above?

You could also take a longer look at `Math.ceil` documentation on the MDN... — Serge K., Aug 21 '17 at 09:27
Write some code that combines `Math.ceil()` and `toFixed()` and if that doesn't work as you expect, put your code in your question. Then others can help you, instead of just writing your code for you. — Kokodoko, Aug 21 '17 at 09:28
if you tried reading documentation, you could've come across the MDN documentation, that may have a function or two to help in your quest - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/ceil#Decimal_adjustment — Jaromanda X, Aug 21 '17 at 09:29
I do not think this is homework. Just browse through the other contributions of this user — Tobias Gassmann, Aug 21 '17 at 09:37
@Script47 it's not homework, I'm just rubbish at math! Thanks for the help everyone the working answer is below. — Janey, Aug 21 '17 at 10:04
This question is indeed a duplicate of "How to round up in Javascript", but it is *not* a duplicate of "Round to at most 2 decimal places (only if necessary)" — Tobias Gassmann, Aug 21 '17 at 10:19

score 10 · Accepted Answer · answered Aug 21 '17 at 09:28

You could use a factor for multiplication with ten and the power of the wanted decimal count and then round it and adjust the dot.

function up(v, n) {
    return Math.ceil(v * Math.pow(10, n)) / Math.pow(10, n);
}

console.log(up(13.4178, 0));
console.log(up(13.4178, 1));
console.log(up(13.4178, 2));

score 0 · Answer 2 · answered Aug 21 '17 at 09:29

Just multiply, round up and divide by a factor of 10^dec.

function roundUp( num, dec ) {
  // raise by dec, default to 0 decimals at the and.
  const d = Math.pow( 10, ( dec || 0 ) );
  // Multiply, round up and divide back so your decimals remain the same
  return Math.ceil( num * d ) / d;
}

console.log( roundUp( 1.2345 ) );
console.log( roundUp( 1.2345, 1 ) );
console.log( roundUp( 1.2345, 2 ) );
console.log( roundUp( 1.2345, 3 ) );

score 0 · Answer 3 · edited May 04 '21 at 22:13

0

Use auxiliary multiplication and division:

function MyCeil(number, digits) {
  var factor = Math.pow(10, digits);
  return Math.ceil(number*factor) / factor;
}

edited May 04 '21 at 22:13

Dan Atkinson

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answered Aug 21 '17 at 09:32

Alexander

4,420
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Javascript always round up to X decimal places

3 Answers3