how to round to 2 decimal places with typescript?

Question

I need to write a function in TypeScript which can round a number to 2 decimal places. For example:

123.456 => should return 123.46

123.3210 => should return 123.32

Can you identify the TypeScript function that I can use to accomplish this? Alternatively, is there is a commonly used third party library used for this, then what library and function should I use?

Does this answer your question? [Format number to always show 2 decimal places](https://stackoverflow.com/questions/6134039/format-number-to-always-show-2-decimal-places) — Baruch, Dec 25 '19 at 16:26
Does this answer your question? [Round to at most 2 decimal places (only if necessary)](https://stackoverflow.com/questions/11832914/round-to-at-most-2-decimal-places-only-if-necessary) — chrisbyte, Dec 25 '19 at 16:27

score 19 · Answer 1 · answered Jun 30 '21 at 09:20

You can use toFixed, it rounds but it returns a string. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/toFixed

So your function body will most likely end up with something like

function round(num: number, fractionDigits: number): number {
    return Number(num.toFixed(fractionDigits));
}

score 5 · Answer 2 · answered Dec 25 '19 at 16:29

5

I have used following code to round to 2 decimal places

(Math.round(val * 100) / 100).toFixed(2);

answered Dec 25 '19 at 16:29

Chamika

129
4

1

this does not compile - "string is not assignable to number".. also try `Math.round(1.005 * 100) / 100` – Boppity Bop Feb 22 '21 at 15:09
The "val" thing is a number. Works like a charm. – Gravity API Aug 28 '21 at 20:38

score 2 · Answer 3 · answered Feb 22 '21 at 15:21

Idk why everything in web-world turns to circus but it seems there is no out-of-the-box solution. I found this blog and it works as far as i could test it:https://expertcodeblog.wordpress.com/2018/02/12/typescript-javascript-round-number-by-decimal-pecision/

  public round(number: number, precision: number) {
    if (precision < 0) {
      let factor = Math.pow(10, precision);
      return Math.round(number * factor) / factor;
    }
    else
      return +(Math.round(Number(number + "e+" + precision)) +
        "e-" + precision);
  }
}

zemil · Answer 4 · 2023-01-22T06:02:47.780

0

For the easiest-to-remember solution but sometimes it can be invalid preceding:

function round(num: number): number {
  return Math.round(num * 100) / 100;
}

For more specific and to ensure things like 1.005 round correctly:

function round(value: number, decimals = 2): number {
    return Number(Math.round(value + 'e' + decimals) + 'e-' + decimals);
}

edited Jan 22 '23 at 06:02

answered Dec 25 '19 at 17:36

zemil

3,235
2
24
33

this doesnt work. read the blogs. `Math.round(1.005 * 100) / 100` – Boppity Bop Feb 22 '21 at 15:13

how to round to 2 decimal places with typescript?

4 Answers4