Remove insignificant trailing zeros from a number?

Question

I had a similar instance where I wanted to use .toFixed() where necessary, but I didn't want the padding when it wasn't. So I ended up using parseFloat in conjunction with toFixed.

toFixed without padding

parseFloat(n.toFixed(4));

Another option that does almost the same thing
This answer may help your decision

Number(n.toFixed(4));

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toFixed will round/pad the number to a specific length, but also convert it to a string. Converting that back to a numeric type will not only make the number safer to use arithmetically, but also automatically drop any trailing 0's. For example:

var n = "1.234000";
    n = parseFloat(n);
 // n is 1.234 and in number form

Because even if you define a number with trailing zeros they're dropped.

var n = 1.23000;
 // n == 1.23;

If you convert it to a string it will not display any trailing zeros, which aren't stored in the variable in the first place since it was created as a Number, not a String.

var n = 1.245000
var noZeroes = n.toString() // "1.245" 

I first used a combination of matti-lyra and gary's answers:

r=(+n).toFixed(4).replace(/\.0+$/,'')

Results:

• 1234870.98762341: "1234870.9876"
• 1230009100: "1230009100"
• 0.0012234: "0.0012"
• 0.1200234: "0.12"
• 0.000001231: "0"
• 0.10001: "0.1000"
• "asdf": "NaN" (so no runtime error)

The somewhat problematic case is 0.10001. I ended up using this longer version:

    r = (+n).toFixed(4);
    if (r.match(/\./)) {
      r = r.replace(/\.?0+$/, '');
    }

• 1234870.98762341: "1234870.9876"
• 1230009100: "1230009100"
• 0.0012234: "0.0012"
• 0.1200234: "0.12"
• 0.000001231: "0"
• 0.10001: "0.1"
• "asdf": "NaN" (so no runtime error)

Update: And this is Gary's newer version (see comments):

r=(+n).toFixed(4).replace(/([0-9]+(\.[0-9]+[1-9])?)(\.?0+$)/,'$1')

This gives the same results as above.

The toFixed method will do the appropriate rounding if necessary. It will also add trailing zeroes, which is not always ideal.

(4.55555).toFixed(2);
//-> "4.56"

(4).toFixed(2);
//-> "4.00"

If you cast the return value to a number, those trailing zeroes will be dropped. This is a simpler approach than doing your own rounding or truncation math.

+(4.55555).toFixed(2);
//-> 4.56

+(4).toFixed(2);
//-> 4

How about just multiplying by one like this?

var x = 1.234000*1; // becomes 1.234

var y = 1.234001*1; // stays as 1.234001

I had the basically the same requirement, and found that there is no built-in mechanism for this functionality.

In addition to trimming the trailing zeros, I also had the need to round off and format the output for the user's current locale (i.e. 123,456.789).

All of my work on this has been included as prettyFloat.js (MIT Licensed) on GitHub: https://github.com/dperish/prettyFloat.js

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Usage Examples:

prettyFloat(1.111001, 3) // "1.111"
prettyFloat(1.111001, 4) // "1.111"
prettyFloat(1.1111001, 5) // "1.1111"
prettyFloat(1234.5678, 2) // "1234.57"
prettyFloat(1234.5678, 2, true) // "1,234.57" (en-us)

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Updated - August, 2018

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All modern browsers now support the ECMAScript Internationalization API, which provides language sensitive string comparison, number formatting, and date and time formatting.

let formatters = {
    default: new Intl.NumberFormat(),
    currency: new Intl.NumberFormat('en-US', { style: 'currency', currency: 'USD', minimumFractionDigits: 0, maximumFractionDigits: 0 }),
    whole: new Intl.NumberFormat('en-US', { style: 'decimal', minimumFractionDigits: 0, maximumFractionDigits: 0 }),
    oneDecimal: new Intl.NumberFormat('en-US', { style: 'decimal', minimumFractionDigits: 1, maximumFractionDigits: 1 }),
    twoDecimal: new Intl.NumberFormat('en-US', { style: 'decimal', minimumFractionDigits: 2, maximumFractionDigits: 2 })
};

formatters.twoDecimal.format(1234.5678);  // result: "1,234.57"
formatters.currency.format(28761232.291); // result: "$28,761,232"

For older browsers, you can use this polyfill: https://cdn.polyfill.io/v2/polyfill.min.js?features=Intl.~locale.en