Intl.NumberFormat() constructor
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since September 2017.
The Intl.NumberFormat()
constructor creates Intl.NumberFormat
objects.
Try it
Syntax
new Intl.NumberFormat()
new Intl.NumberFormat(locales)
new Intl.NumberFormat(locales, options)
Intl.NumberFormat()
Intl.NumberFormat(locales)
Intl.NumberFormat(locales, options)
Note: Intl.NumberFormat()
can be called with or without new
. Both create a new Intl.NumberFormat
instance. However, there's a special behavior when it's called without new
and the this
value is another Intl.NumberFormat
instance; see Return value.
Parameters
locales
Optional-
A string with a BCP 47 language tag or an
Intl.Locale
instance, or an array of such locale identifiers. The runtime's default locale is used whenundefined
is passed or when none of the specified locale identifiers is supported. For the general form and interpretation of thelocales
argument, see the parameter description on theIntl
main page.The following Unicode extension key is allowed:
nu
-
See
numberingSystem
.
This key can also be set with
options
(as listed below). When both are set, theoptions
property takes precedence. options
Optional-
An object. For ease of reading, the property list is broken into sections based on their purposes, including locale options, style options, digit options, and other options.
Locale options
localeMatcher
-
The locale matching algorithm to use. Possible values are
"lookup"
and"best fit"
; the default is"best fit"
. For information about this option, see Locale identification and negotiation. numberingSystem
-
The numbering system to use for number formatting, such as
"arab"
,"hans"
,"mathsans"
, and so on. For a list of supported numbering system types, seeIntl.Locale.prototype.getNumberingSystems()
. This option can also be set through thenu
Unicode extension key; if both are provided, thisoptions
property takes precedence.
Style options
Depending on the style
used, some of them may be ignored, and others may be required:
style
-
The formatting style to use.
"decimal"
(default)-
For plain number formatting.
"currency"
-
For currency formatting.
"percent"
-
For percent formatting.
"unit"
-
For unit formatting.
currency
-
The currency to use in currency formatting. Possible values are the ISO 4217 currency codes, such as
"USD"
for the US dollar,"EUR"
for the euro, or"CNY"
for the Chinese RMB — see the Current currency & funds code list. There is no default value; if thestyle
is"currency"
, thecurrency
property must be provided. It is normalized to uppercase. currencyDisplay
-
How to display the currency in currency formatting.
"code"
-
Use the ISO currency code.
"symbol"
(default)-
Use a localized currency symbol such as €.
"narrowSymbol"
-
Use a narrow format symbol ("$100" rather than "US$100").
"name"
-
Use a localized currency name such as
"dollar"
.
currencySign
-
In many locales, accounting format means to wrap the number with parentheses instead of appending a minus sign. Possible values are
"standard"
and"accounting"
; the default is"standard"
. unit
-
The unit to use in
unit
formatting, Possible values are core unit identifiers, defined in UTS #35, Part 2, Section 6. A subset of units from the full list was selected for use in ECMAScript. Pairs of simple units can be concatenated with "-per-" to make a compound unit. There is no default value; if thestyle
is"unit"
, theunit
property must be provided. unitDisplay
-
The unit formatting style to use in
unit
formatting. Possible values are:
Digit options
The following properties are also supported by Intl.PluralRules
.
minimumIntegerDigits
-
The minimum number of integer digits to use. A value with a smaller number of integer digits than this number will be left-padded with zeros (to the specified length) when formatted. Possible values are from
1
to21
; the default is1
. minimumFractionDigits
-
The minimum number of fraction digits to use. Possible values are from
0
to100
; the default for plain number and percent formatting is0
; the default for currency formatting is the number of minor unit digits provided by the ISO 4217 currency code list (2 if the list doesn't provide that information). See SignificantDigits/FractionDigits default values for when this default gets applied. maximumFractionDigits
-
The maximum number of fraction digits to use. Possible values are from
0
to100
; the default for plain number formatting is the larger ofminimumFractionDigits
and3
; the default for currency formatting is the larger ofminimumFractionDigits
and the number of minor unit digits provided by the ISO 4217 currency code list (2 if the list doesn't provide that information); the default for percent formatting is the larger ofminimumFractionDigits
and 0. See SignificantDigits/FractionDigits default values for when this default gets applied. minimumSignificantDigits
-
The minimum number of significant digits to use. Possible values are from
1
to21
; the default is1
. See SignificantDigits/FractionDigits default values for when this default gets applied. maximumSignificantDigits
-
The maximum number of significant digits to use. Possible values are from
1
to21
; the default is21
. See SignificantDigits/FractionDigits default values for when this default gets applied. roundingPriority
-
Specify how rounding conflicts will be resolved if both "FractionDigits" (
minimumFractionDigits
/maximumFractionDigits
) and "SignificantDigits" (minimumSignificantDigits
/maximumSignificantDigits
) are specified. Possible values are:"auto"
(default)-
The result from the significant digits property is used.
"morePrecision"
-
The result from the property that results in more precision is used.
"lessPrecision"
-
The result from the property that results in less precision is used.
The value
"auto"
is normalized to"morePrecision"
ifnotation
is"compact"
and none of the four "FractionDigits"/"SignificantDigits" options are set.Note that for values other than
auto
the result with more precision is calculated from themaximumSignificantDigits
andmaximumFractionDigits
(minimum fractional and significant digit settings are ignored). roundingIncrement
-
Indicates the increment at which rounding should take place relative to the calculated rounding magnitude. Possible values are
1
,2
,5
,10
,20
,25
,50
,100
,200
,250
,500
,1000
,2000
,2500
, and5000
; the default is1
. It cannot be mixed with significant-digits rounding or any setting ofroundingPriority
other thanauto
. roundingMode
-
How decimals should be rounded. Possible values are:
"ceil"
-
Round toward +∞. Positive values round up. Negative values round "more positive".
"floor"
-
Round toward -∞. Positive values round down. Negative values round "more negative".
"expand"
-
round away from 0. The magnitude of the value is always increased by rounding. Positive values round up. Negative values round "more negative".
"trunc"
-
Round toward 0. This magnitude of the value is always reduced by rounding. Positive values round down. Negative values round "less negative".
"halfCeil"
-
ties toward +∞. Values above the half-increment round like
"ceil"
(towards +∞), and below like"floor"
(towards -∞). On the half-increment, values round like"ceil"
. "halfFloor"
-
Ties toward -∞. Values above the half-increment round like
"ceil"
(towards +∞), and below like"floor"
(towards -∞). On the half-increment, values round like"floor"
. "halfExpand"
(default)-
Ties away from 0. Values above the half-increment round like
"expand"
(away from zero), and below like"trunc"
(towards 0). On the half-increment, values round like"expand"
. "halfTrunc"
-
Ties toward 0. Values above the half-increment round like
"expand"
(away from zero), and below like"trunc"
(towards 0). On the half-increment, values round like"trunc"
. "halfEven"
-
Ties towards the nearest even integer. Values above the half-increment round like
"expand"
(away from zero), and below like"trunc"
(towards 0). On the half-increment values round towards the nearest even digit.
These options reflect the ICU user guide, where "expand" and "trunc" map to ICU "UP" and "DOWN", respectively. The rounding modes example below demonstrates how each mode works.
trailingZeroDisplay
-
The strategy for displaying trailing zeros on whole numbers. Possible values are:
"auto"
(default)-
Keep trailing zeros according to
minimumFractionDigits
andminimumSignificantDigits
. "stripIfInteger"
-
Remove the fraction digits if they are all zero. This is the same as
"auto"
if any of the fraction digits is non-zero.
SignificantDigits/FractionDigits default values
For the four options above (the FractionDigits
and SignificantDigits
options), we mentioned their defaults; however, these defaults are not unconditionally applied. They are only applied when the property is actually going to be used, which depends on the roundingPriority
and notation
settings. Specifically:
- If
roundingPriority
is not"auto"
, then all four options apply. - If
roundingPriority
is"auto"
and at least oneSignificantDigits
option is set, then theSignificantDigits
options apply and theFractionDigits
options are ignored. - If
roundingPriority
is"auto"
, and either at least oneFractionDigits
option is set ornotation
is not"compact"
, then theFractionDigits
options apply and theSignificantDigits
options are ignored. - If
roundingPriority
is"auto"
,notation
is"compact"
, and none of the four options are set, then they are set to{ minimumFractionDigits: 0, maximumFractionDigits: 0, minimumSignificantDigits: 1, maximumSignificantDigits: 2 }
, regardless of the defaults mentioned above, androundingPriority
is set to"morePrecision"
.
Other options
notation
-
The formatting that should be displayed for the number. Possible values are:
"standard"
(default)-
Plain number formatting.
"scientific"
-
Return the order-of-magnitude for formatted number.
"engineering"
-
Return the exponent of ten when divisible by three.
"compact"
-
String representing exponent; defaults to using the "short" form.
compactDisplay
-
Only used when
notation
is"compact"
. Possible values are"short"
and"long"
; the default is"short"
. useGrouping
-
Whether to use grouping separators, such as thousands separators or thousand/lakh/crore separators.
"always"
-
Display grouping separators even if the locale prefers otherwise.
"auto"
-
Display grouping separators based on the locale preference, which may also be dependent on the currency.
"min2"
-
Display grouping separators when there are at least 2 digits in a group.
true
-
Same as
"always"
. false
-
Display no grouping separators.
The default is
"min2"
ifnotation
is"compact"
, and"auto"
otherwise. The string values"true"
and"false"
are accepted, but are always converted to the default value. signDisplay
-
When to display the sign for the number. Possible values are:
"auto"
(default)-
Sign display for negative numbers only, including negative zero.
"always"
-
Always display sign.
"exceptZero"
-
Sign display for positive and negative numbers, but not zero.
"negative"
-
Sign display for negative numbers only, excluding negative zero.
"never"
-
Never display sign.
Return value
A new Intl.NumberFormat
object.
Note: The text below describes behavior that is marked by the specification as "optional". It may not work in all environments. Check the browser compatibility table.
Normally, Intl.NumberFormat()
can be called with or without new
, and a new Intl.NumberFormat
instance is returned in both cases. However, if the this
value is an object that is instanceof
Intl.NumberFormat
(doesn't necessarily mean it's created via new Intl.NumberFormat
; just that it has Intl.NumberFormat.prototype
in its prototype chain), then the value of this
is returned instead, with the newly created Intl.NumberFormat
object hidden in a [Symbol(IntlLegacyConstructedSymbol)]
property (a unique symbol that's reused between instances).
const formatter = Intl.NumberFormat.call(
{ __proto__: Intl.NumberFormat.prototype },
"en-US",
{ notation: "scientific" },
);
console.log(Object.getOwnPropertyDescriptors(formatter));
// {
// [Symbol(IntlLegacyConstructedSymbol)]: {
// value: NumberFormat [Intl.NumberFormat] {},
// writable: false,
// enumerable: false,
// configurable: false
// }
// }
Note that there's only one actual Intl.NumberFormat
instance here: the one hidden in [Symbol(IntlLegacyConstructedSymbol)]
. Calling the format()
and resolvedOptions()
methods on formatter
would correctly use the options stored in that instance, but calling all other methods (e.g. formatRange()
) would fail with "TypeError: formatRange method called on incompatible Object", because those methods don't consult the hidden instance's options.
This behavior, called ChainNumberFormat
, does not happen when Intl.NumberFormat()
is called without new
but with this
set to anything else that's not an instanceof Intl.NumberFormat
. If you call it directly as Intl.NumberFormat()
, the this
value is Intl
, and a new Intl.NumberFormat
instance is created normally.
Exceptions
RangeError
-
Thrown in one of the following cases:
- A property that takes enumerated values (such as
style
,units
,currency
, and so on) is set to an invalid value. -
Both
maximumFractionDigits
andminimumFractionDigits
are set, and they are set to different values. Note that depending on various formatting options, these properties can have default values. It is therefore possible to get this error even if you only set one of the properties.
- A property that takes enumerated values (such as
TypeError
-
Thrown if the
options.style
property is set to "unit" or "currency", and no value has been set for the corresponding propertyoptions.unit
oroptions.currency
.
Examples
Basic usage
In basic use without specifying a locale, a formatted string in the default locale and with default options is returned.
const amount = 3500;
console.log(new Intl.NumberFormat().format(amount));
// '3,500' if in US English locale
Decimal and percent formatting
const amount = 3500;
new Intl.NumberFormat("en-US", {
style: "decimal",
}).format(amount); // '3,500'
new Intl.NumberFormat("en-US", {
style: "percent",
}).format(amount); // '350,000%'
Unit formatting
If the style
is 'unit'
, a unit
property must be provided.
Optionally, unitDisplay
controls the unit formatting.
const amount = 3500;
new Intl.NumberFormat("en-US", {
style: "unit",
unit: "liter",
}).format(amount); // '3,500 L'
new Intl.NumberFormat("en-US", {
style: "unit",
unit: "liter",
unitDisplay: "long",
}).format(amount); // '3,500 liters'
Currency formatting
If the style
is 'currency'
, a currency
property
must be provided. Optionally, currencyDisplay
and
currencySign
control the unit formatting.
const amount = -3500;
new Intl.NumberFormat("en-US", {
style: "currency",
currency: "USD",
}).format(amount); // '-$3,500.00'
new Intl.NumberFormat("bn", {
style: "currency",
currency: "USD",
currencyDisplay: "name",
}).format(amount); // '-3,500.00 US dollars'
new Intl.NumberFormat("bn", {
style: "currency",
currency: "USD",
currencySign: "accounting",
}).format(amount); // '($3,500.00)'
Scientific, engineering or compact notations
Scientific and compact notation are represented by the notation
option and can be formatted like this:
new Intl.NumberFormat("en-US", {
notation: "scientific",
}).format(987654321);
// 9.877E8
new Intl.NumberFormat("pt-PT", {
notation: "scientific",
}).format(987654321);
// 9,877E8
new Intl.NumberFormat("en-GB", {
notation: "engineering",
}).format(987654321);
// 987.654E6
new Intl.NumberFormat("de", {
notation: "engineering",
}).format(987654321);
// 987,654E6
new Intl.NumberFormat("zh-CN", {
notation: "compact",
}).format(987654321);
// 9.9亿
new Intl.NumberFormat("fr", {
notation: "compact",
compactDisplay: "long",
}).format(987654321);
// 988 millions
new Intl.NumberFormat("en-GB", {
notation: "compact",
compactDisplay: "short",
}).format(987654321);
// 988M
Displaying signs
Display a sign for positive and negative numbers, but not zero:
new Intl.NumberFormat("en-US", {
style: "percent",
signDisplay: "exceptZero",
}).format(0.55);
// '+55%'
Note that when the currency sign is "accounting", parentheses might be used instead of a minus sign:
new Intl.NumberFormat("bn", {
style: "currency",
currency: "USD",
currencySign: "accounting",
signDisplay: "always",
}).format(-3500);
// '($3,500.00)'
FractionDigits, SignificantDigits and IntegerDigits
You can specify the minimum or maximum number of fractional, integer or significant digits to display when formatting a number.
Note: If both significant and fractional digit limits are specified, then the actual formatting depends on the roundingPriority
.
Using FractionDigits and IntegerDigits
The integer and fraction digit properties indicate the number of digits to display before and after the decimal point, respectively. If the value to display has fewer integer digits than specified, it will be left-padded with zeros to the expected number. If it has fewer fractional digits, it will be right-padded with zeros. Both cases are shown below:
// Formatting adds zeros to display minimum integers and fractions
console.log(
new Intl.NumberFormat("en", {
minimumIntegerDigits: 3,
minimumFractionDigits: 4,
}).format(4.33),
);
// "004.3300"
If a value has more fractional digits than the specified maximum number, it will be rounded.
The way that it is rounded depends on the roundingMode
property (more details are provided in the rounding modes section).
Below the value is rounded from five fractional digits (4.33145
) to two (4.33
):
// Display value shortened to maximum number of digits
console.log(
new Intl.NumberFormat("en", {
maximumFractionDigits: 2,
}).format(4.33145),
);
// "4.33"
The minimum fractional digits have no effect if the value already has more than 2 fractional digits:
// Minimum fractions have no effect if value is higher precision.
console.log(
new Intl.NumberFormat("en", {
minimumFractionDigits: 2,
}).format(4.33145),
);
// "4.331"
Warning: Watch out for default values as they may affect formatting even if not specified in your code.
The default maximum digit value is 3
for plain values, 2
for currency, and may have different values for other predefined types.
The formatted value above is rounded to 3 digits, even though we didn't specify the maximum digits!
This is because a default value of maximumFractionDigits
is set when we specify minimumFractionDigits
, and visa versa. The default values of maximumFractionDigits
and minimumFractionDigits
are 3
and 0
, respectively.
You can use resolvedOptions()
to inspect the formatter.
console.log(
new Intl.NumberFormat("en", {
maximumFractionDigits: 2,
}).resolvedOptions(),
);
// {
// …
// minimumIntegerDigits: 1,
// minimumFractionDigits: 0,
// maximumFractionDigits: 2,
// …
// }
console.log(
new Intl.NumberFormat("en", {
minimumFractionDigits: 2,
}).resolvedOptions(),
);
// {
// …
// minimumIntegerDigits: 1,
// minimumFractionDigits: 2,
// maximumFractionDigits: 3,
// …
// }
Using SignificantDigits
The number of significant digits is the total number of digits including both integer and fractional parts.
The maximumSignificantDigits
is used to indicate the total number of digits from the original value to display.
The examples below show how this works. Note in particular the last case: only the first digit is retained and the others are discarded/set to zero.
// Display 5 significant digits
console.log(
new Intl.NumberFormat("en", {
maximumSignificantDigits: 5,
}).format(54.33145),
);
// "54.331"
// Max 2 significant digits
console.log(
new Intl.NumberFormat("en", {
maximumSignificantDigits: 2,
}).format(54.33145),
);
// "54"
// Max 1 significant digits
console.log(
new Intl.NumberFormat("en", {
maximumSignificantDigits: 1,
}).format(54.33145),
);
// "50"
The minimumSignificantDigits
ensures that at least the specified number of digits are displayed, adding zeros to the end of the value if needed.
// Minimum 10 significant digits
console.log(
new Intl.NumberFormat("en", {
minimumSignificantDigits: 10,
}).format(54.33145),
);
// "54.33145000"
Warning: Watch out for default values as they may affect formatting.
If only one SignificantDigits
property is used, then its counterpart will automatically be applied with the default value.
The default maximum and minimum significant digit values are 20 and 1, respectively.
Specifying significant and fractional digits at the same time
The fraction digits (minimumFractionDigits
/maximumFractionDigits
) and significant digits (minimumSignificantDigits
/maximumSignificantDigits
) are both ways of controlling how many fractional and leading digits should be formatted.
If both are used at the same time, it is possible for them to conflict.
These conflicts are resolved using the roundingPriority
property.
By default, this has a value of "auto"
, which means that if either minimumSignificantDigits
or maximumSignificantDigits
is specified, the fractional and integer digit properties will be ignored.
For example, the code below formats the value of 4.33145
with maximumFractionDigits: 3
, and then maximumSignificantDigits: 2
, and then both.
The value with both is the one set with maximumSignificantDigits
.
console.log(
new Intl.NumberFormat("en", {
maximumFractionDigits: 3,
}).format(4.33145),
);
// "4.331"
console.log(
new Intl.NumberFormat("en", {
maximumSignificantDigits: 2,
}).format(4.33145),
);
// "4.3"
console.log(
new Intl.NumberFormat("en", {
maximumFractionDigits: 3,
maximumSignificantDigits: 2,
}).format(4.33145),
);
// "4.3"
Using resolvedOptions()
to inspect the formatter, we can see that the returned object does not include maximumFractionDigits
when maximumSignificantDigits
or minimumSignificantDigits
are specified.
console.log(
new Intl.NumberFormat("en", {
maximumFractionDigits: 3,
maximumSignificantDigits: 2,
}).resolvedOptions(),
);
// {
// …
// minimumIntegerDigits: 1,
// minimumSignificantDigits: 1,
// maximumSignificantDigits: 2,
// …
// }
console.log(
new Intl.NumberFormat("en", {
maximumFractionDigits: 3,
minimumSignificantDigits: 2,
}).resolvedOptions(),
);
// {
// …
// minimumIntegerDigits: 1,
// minimumSignificantDigits: 2,
// maximumSignificantDigits: 21,
// …
// }
In addition to "auto"
, you can resolve conflicts by specifying roundingPriority
as "morePrecision"
or "lessPrecision"
.
The formatter calculates the precision using the values of maximumSignificantDigits
and maximumFractionDigits
.
The code below shows the format being selected for the three different rounding priorities:
const maxFracNF = new Intl.NumberFormat("en", {
maximumFractionDigits: 3,
});
console.log(`maximumFractionDigits:3 - ${maxFracNF.format(1.23456)}`);
// "maximumFractionDigits:2 - 1.235"
const maxSigNS = new Intl.NumberFormat("en", {
maximumSignificantDigits: 3,
});
console.log(`maximumSignificantDigits:3 - ${maxSigNS.format(1.23456)}`);
// "maximumSignificantDigits:3 - 1.23"
const bothAuto = new Intl.NumberFormat("en", {
maximumSignificantDigits: 3,
maximumFractionDigits: 3,
});
console.log(`auto - ${bothAuto.format(1.23456)}`);
// "auto - 1.23"
const bothLess = new Intl.NumberFormat("en", {
roundingPriority: "lessPrecision",
maximumSignificantDigits: 3,
maximumFractionDigits: 3,
});
console.log(`lessPrecision - ${bothLess.format(1.23456)}`);
// "lessPrecision - 1.23"
const bothMore = new Intl.NumberFormat("en", {
roundingPriority: "morePrecision",
maximumSignificantDigits: 3,
maximumFractionDigits: 3,
});
console.log(`morePrecision - ${bothMore.format(1.23456)}`);
// "morePrecision - 1.235"
Note that the algorithm can behave in an unintuitive way if a minimum value is specified without a maximum value.
The example below formats the value 1
specifying minimumFractionDigits: 2
(formatting to 1.00
) and minimumSignificantDigits: 2
(formatting to 1.0
).
Since 1.00
has more digits than 1.0
, this should be the result when prioritizing morePrecision
, but in fact the opposite is true:
const bothLess = new Intl.NumberFormat("en", {
roundingPriority: "lessPrecision",
minimumFractionDigits: 2,
minimumSignificantDigits: 2,
});
console.log(`lessPrecision - ${bothLess.format(1)}`);
// "lessPrecision - 1.00"
const bothMore = new Intl.NumberFormat("en", {
roundingPriority: "morePrecision",
minimumFractionDigits: 2,
minimumSignificantDigits: 2,
});
console.log(`morePrecision - ${bothMore.format(1)}`);
// "morePrecision - 1.0"
The reason for this is that only the "maximum precision" values are used for the calculation, and the default value of maximumSignificantDigits
is much higher than maximumFractionDigits
.
Note: The working group have proposed a modification of the algorithm where the formatter should evaluate the result of using the specified fractional and significant digits independently (taking account of both minimum and maximum values).
It will then select the option that displays more fractional digits if morePrecision
is set, and fewer if lessPrecision
is set.
This will result in more intuitive behavior for this case.
Rounding modes
If a value has more fractional digits than allowed by the constructor options, the formatted value will be rounded to the specified number of fractional digits.
The way in which the value is rounded depends on the roundingMode
property.
Number formatters use halfExpand
rounding by default, which rounds values "away from zero" at the half-increment (in other words, the magnitude of the value is rounded up).
For a positive number, if the fractional digits to be removed are closer to the next increment (or on the half way point) then the remaining fractional digits will be rounded up, otherwise they are rounded down. This is shown below: 2.23 rounded to two significant digits is truncated to 2.2 because 2.23 is less than the half increment 2.25, while values of 2.25 and greater are rounded up to 2.3:
// Value below half-increment: round down.
console.log(
new Intl.NumberFormat("en", {
maximumSignificantDigits: 2,
}).format(2.23),
);
// "2.2"
// Value on or above half-increment: round up.
console.log(
new Intl.NumberFormat("en", {
maximumSignificantDigits: 2,
}).format(2.25),
);
console.log(
new Intl.NumberFormat("en", {
maximumSignificantDigits: 2,
}).format(2.28),
);
// "2.3"
// "2.3"
A negative number on or below the half-increment point is also rounded away from zero (becomes more negative):
// Value below half-increment: round down.
console.log(
new Intl.NumberFormat("en", {
maximumSignificantDigits: 2,
}).format(-2.23),
);
// "-2.2"
// Value on or above half-increment: round up.
console.log(
new Intl.NumberFormat("en", {
maximumSignificantDigits: 2,
}).format(-2.25),
);
console.log(
new Intl.NumberFormat("en", {
maximumSignificantDigits: 2,
}).format(-2.28),
);
// "-2.3"
// "-2.3"
The table below show the effect of different rounding modes for positive and negative values that are on and around the half-increment.
rounding mode | 2.23 | 2.25 | 2.28 | -2.23 | -2.25 | -2.28 |
---|---|---|---|---|---|---|
ceil |
2.3 | 2.3 | 2.3 | -2.2 | -2.2 | -2.2 |
floor |
2.2 | 2.2 | 2.2 | -2.3 | -2.3 | -2.3 |
expand |
2.3 | 2.3 | 2.3 | -2.3 | -2.3 | -2.3 |
trunc |
2.2 | 2.2 | 2.2 | -2.2 | -2.2 | -2.2 |
halfCeil |
2.2 | 2.3 | 2.3 | -2.2 | -2.2 | -2.3 |
halfFloor |
2.2 | 2.2 | 2.3 | -2.2 | -2.3 | -2.3 |
halfExpand |
2.2 | 2.3 | 2.3 | -2.2 | -2.3 | -2.3 |
halfTrunc |
2.2 | 2.2 | 2.3 | -2.2 | -2.2 | -2.3 |
halfEven |
2.2 | 2.2 | 2.3 | -2.2 | -2.2 | -2.3 |
When using halfEven
, its behavior also depends on the parity (odd or even) of the last digit of the rounded number. For example, the behavior of halfEven
in the table above is the same as halfTrunc
, because the magnitudes of all numbers are between a smaller "even" number (2.2) and a larger "odd" number (2.3). If the numbers are between ±2.3 and ±2.4, halfEven
will behave like halfExpand
instead. This behavior avoids consistently under- or over-estimating half-increments in a large data sample.
Using roundingIncrement
Sometimes we want to round the remaining fractional digits to some other increment than the next integer. For example, currencies for which the smallest coin is 5 cents might want to round the value to increments of 5, reflecting amounts that can actually be paid in cash.
This kind of rounding can be achieved with the roundingIncrement
property.
For example, if maximumFractionDigits
is 2 and roundingIncrement
is 5, then the number is rounded to the nearest 0.05:
const nf = new Intl.NumberFormat("en-US", {
style: "currency",
currency: "USD",
maximumFractionDigits: 2,
roundingIncrement: 5,
});
console.log(nf.format(11.29)); // "$11.30"
console.log(nf.format(11.25)); // "$11.25"
console.log(nf.format(11.22)); // "$11.20"
This particular pattern is referred to as "nickel rounding", where nickel is the colloquial name for a USA 5 cent coin.
To round to the nearest 10 cents ("dime rounding"), you could change roundingIncrement
to 10
.
const nf = new Intl.NumberFormat("en-US", {
style: "currency",
currency: "USD",
maximumFractionDigits: 2,
roundingIncrement: 5,
});
console.log(nf.format(11.29)); // "$11.30"
console.log(nf.format(11.25)); // "$11.25"
console.log(nf.format(11.22)); // "$11.20"
You can also use roundingMode
to change the rounding algorithm.
The example below shows how halfCeil
rounding can be used to round the value "less positive" below the half-rounding increment and "more positive" if above or on the half-increment.
The incremented digit is "0.05" so the half-increment is at .025 (below, this is shown at 11.225).
const nf = new Intl.NumberFormat("en-US", {
style: "currency",
currency: "USD",
maximumFractionDigits: 2,
roundingIncrement: 5,
roundingMode: "halfCeil",
});
console.log(nf.format(11.21)); // "$11.20"
console.log(nf.format(11.22)); // "$11.20"
console.log(nf.format(11.224)); // "$11.20"
console.log(nf.format(11.225)); // "$11.25"
console.log(nf.format(11.23)); // "$11.25"
If you need to change the number of digits, remember that minimumFractionDigits
and maximumFractionDigits
must both be set to the same value, or a RangeError
is thrown.
roundingIncrement
cannot be mixed with significant-digits rounding or any setting of roundingPriority
other than auto
.
Specifications
Specification |
---|
ECMAScript Internationalization API Specification # sec-intl-numberformat-constructor |
Browser compatibility
BCD tables only load in the browser