toFixed function on large numbers

Question

I have following number with e+ on it

9.074701047887939e+304

I want to take only 9.07

So I tried below , but its not working , its returning full output

console.log(parseFloat(9.074701047887939e+304).toFixed(2));

Ps : I also need the code to work for normal numbers aswell for example 892.0747010 , should output 892.07

so for `9.1` and `9.1e+304`, what do you want as the result? — nonopolarity, Jan 18 '20 at 08:59
console.log((parseFloat(9.074701047887939e+304).toPrecision(3)).substr(0,4)); — Hamid Shoja, Jan 18 '20 at 09:05
see: https://stackoverflow.com/questions/18719775/parsing-and-converting-exponential-values-to-decimal-in-javascript — Hamid Shoja, Jan 18 '20 at 09:06
it also depends on what you want for `9.074701047887939e-304` as well. Please see updated answer, including negative numbers — nonopolarity, Jan 18 '20 at 09:29

CertainPerformance · Answer 1 · 2020-01-18T08:58:58.157

3

toFixed trims digits after the decimal point, but your actual number is very large - it doesn't have a decimal point.

If you don't know in advance whether the number is large or not, one option is to call toFixed(2) on the number first (trimming off and properly rounding digits past the decimal point for small numbers), then using a regular expression to take the numeric part only (removing the e if it exists), then call toFixed(2) again (trimming off and properly rounding digits past the decimal point for large numbers):

const fix = num => Number(
  num.toFixed(2).match(/\d+(?:\.\d+)?/)[0]
).toFixed(2);

console.log(fix(9.074701047887939e+304));
console.log(fix(123.4567));
console.log(fix(12345));

edited Jan 18 '20 at 08:58

answered Jan 18 '20 at 08:39

CertainPerformance

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You can adjust the solution, maybe implement it as "remove everything from two digits after the decimal onwards", and use `(bignumber).toString().replace(/(\.\d\d).*/,"$1")` – Niet the Dark Absol Jan 18 '20 at 08:47
Which is faster , yours or nopole answer ? – Gracie williams Jan 18 '20 at 09:35

nonopolarity · Accepted Answer · 2020-01-18T09:23:28.323

1

Since you mentioned for both 9.074701047887939e+304 and 9.074701047887939, you want the answer to be 9.07.

For 9.074701047887939e-304 I assume you want 9.07 too, although you might actually want 0.00.

const twoDecimal = (a =>
  (a.toString().match(/e/) ? Number(a.toString().match(/[^e]*/)[0]) : a).toFixed(2)
);

console.log(twoDecimal(9.074701047887939e+304));
console.log(twoDecimal(9.074701047887939e-304));
console.log(twoDecimal(9.074701047887939));
console.log(twoDecimal(789.074701047887939));
console.log(twoDecimal(0.00001));
console.log(twoDecimal(0.20001));

console.log(twoDecimal(-9.074701047887939e+304));
console.log(twoDecimal(-9.074701047887939e-304));
console.log(twoDecimal(-9.074701047887939));
console.log(twoDecimal(-789.074701047887939));
console.log(twoDecimal(-0.00001));
console.log(twoDecimal(-0.20001));

console.log(twoDecimal(0));

edited Jan 18 '20 at 09:23

answered Jan 18 '20 at 08:38

nonopolarity

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Its adding e+1 for all numbers – Gracie williams Jan 18 '20 at 08:43
`.toPrecision() ` added – nonopolarity Jan 18 '20 at 08:46
we have different behaviors... his cannot process negative number currently... and his would give `"0.00"` for `-9.074701047887939e-304`. You can try http://jsben.ch/FtNBK for benchmark – nonopolarity Jan 18 '20 at 09:42

toFixed function on large numbers

2 Answers2