The static String.fromCharCode()
method returns a string created from the specified sequence of UTF-16 code units.
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Syntax
String.fromCharCode(num1[, ...[, numN]])
Parameters
num1, ..., numN
- A sequence of numbers that are UTF-16 code units. The range is between
0
and65535
(0xFFFF
). Numbers greater than0xFFFF
are truncated. No validity checks are performed.
Return value
A string of length N
consisting of the N
specified UTF-16 code units.
Description
This method returns a string and not a String
object.
Because fromCharCode()
is a static method of String
, you always use it as String.fromCharCode()
, rather than as a method of a String
object you created.
Returning supplementary characters
In UTF-16, the most common characters can be represented by a single 16-bit value (i.e. a code unit). However, this set of characters, known as the Base Multilingual Plane (BMP), is only 1/17th of the total addressable Unicode code points. The remaining code points, in the range of 65536
(0x010000
) to 1114111
(0x10FFFF
) are known as supplementary characters. In UTF-16, supplementary characters are represented by two 16-bit code units, known as surrogates, that were reserved for this purpose. A valid combination of two surrogates used to represent a supplementary character is known as a surrogate pair.
Because fromCharCode()
only works with 16-bit values (same as the \u
escape sequence), a surrogate pair is required in order to return a supplementary character. For example, both String.fromCharCode(0xD83C, 0xDF03)
and \uD83C\uDF03
return code point U+1F303
"Night with Stars".
While there is a mathematical relationship between the supplementary code point value (e.g. 0x1F303
) and both surrogate values that represent it (e.g., 0xD83C
and 0xDF03
), it does require an extra step to either calculate or look up the surrogate pair values every time a supplementary code point is to be used. For this reason, it's more convenient to use String.fromCodePoint()
(part of the ES2015 standard), which allows for returning supplementary characters based on their actual code point value. For example, String.fromCodePoint(0x1F303)
returns code point U+1F303
"Night with Stars".
Examples
Using fromCharCode()
BMP characters, in UTF-16, use a single code unit:
String.fromCharCode(65, 66, 67); // returns "ABC" String.fromCharCode(0x2014); // returns "—" String.fromCharCode(0x12014); // also returns "—"; the digit 1 is truncated and ignored String.fromCharCode(8212); // also returns "—"; 8212 is the decimal form of 0x2014
Complete UTF 16 Table.
Supplementary characters, in UTF-16, require two code units (i.e. a surrogate pair):
String.fromCharCode(0xD83C, 0xDF03); // Code Point U+1F303 "Night with String.fromCharCode(55356, 57091); // Stars" == "\uD83C\uDF03" String.fromCharCode(0xD834, 0xDF06, 0x61, 0xD834, 0xDF07); // "\uD834\uDF06a\uD834\uDF07"
Specifications
Specification |
---|
ECMAScript (ECMA-262) The definition of 'String.fromCharCode' in that specification. |
Browser compatibility
The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
fromCharCode | Chrome Full support 1 | Edge Full support 12 | Firefox Full support 1 | IE Full support 4 | Opera Full support 4 | Safari Full support 1 | WebView Android Full support 1 | Chrome Android Full support 18 | Firefox Android Full support 4 | Opera Android Full support 10.1 | Safari iOS Full support 1 | Samsung Internet Android Full support 1.0 | nodejs Full support 0.1.100 |
Legend
- Full support
- Full support