String.fromCodePoint()

¥Syntax

String.fromCodePoint()
String.fromCodePoint(num1)
String.fromCodePoint(num1, num2)
String.fromCodePoint(num1, num2, /* …, */ numN)

¥Parameters

num1, …, numN

介于 0 和 0x10FFFF（含）之间的整数，表示 Unicode 代码点。

¥Return value

使用指定的代码点序列创建的字符串。

¥A string created by using the specified sequence of code points.

¥Exceptions

RangeError

如果 numN 不是整数、小于 0、或者转换为数字后大于 0x10FFFF，则抛出此异常。

¥Description

由于 fromCodePoint() 是 String 的静态方法，因此你始终将其用作 String.fromCodePoint()，而不是用作你创建的 String 值的方法。

¥Because fromCodePoint() is a static method of String, you always use it as String.fromCodePoint(), rather than as a method of a String value you created.

Unicode 代码点范围从 0 到 1114111 (0x10FFFF)。在 UTF-16 中，每个字符串索引都是一个值为 0 – 65535 的代码单元。较高的代码点由一对 16 位代理伪字符表示。因此，fromCodePoint() 可能会返回一个字符串，其 length（以 UTF-16 代码单元表示）大于传递的参数数量。有关 Unicode 的信息，请参阅 UTF-16 字符、Unicode 代码点和字素簇。

¥Unicode code points range from 0 to 1114111 (0x10FFFF). In UTF-16, each string index is a code unit with value 0 – 65535. Higher code points are represented by a pair of 16-bit surrogate pseudo-characters. Therefore, fromCodePoint() may return a string whose length (in UTF-16 code units) is larger than the number of arguments passed. For information on Unicode, see UTF-16 characters, Unicode code points, and grapheme clusters.

¥Examples

¥Using fromCodePoint()

有效输入：

¥Valid input:

String.fromCodePoint(42); // "*"
String.fromCodePoint(65, 90); // "AZ"
String.fromCodePoint(0x404); // "\u0404" === "Є"
String.fromCodePoint(0x2f804); // "\uD87E\uDC04"
String.fromCodePoint(194564); // "\uD87E\uDC04"
String.fromCodePoint(0x1d306, 0x61, 0x1d307); // "\uD834\uDF06a\uD834\uDF07"

输入无效：

¥Invalid input:

String.fromCodePoint("_"); // RangeError
String.fromCodePoint(Infinity); // RangeError
String.fromCodePoint(-1); // RangeError
String.fromCodePoint(3.14); // RangeError
String.fromCodePoint(3e-2); // RangeError
String.fromCodePoint(NaN); // RangeError

¥Compared to fromCharCode()

String.fromCharCode() 无法通过指定代码点来返回增补字符（即代码点 0x010000 – 0x10FFFF）。相反，它需要 UTF-16 代理对才能返回补充字符：

¥String.fromCharCode() cannot return supplementary characters (i.e. code points 0x010000 – 0x10FFFF) by specifying their code point. Instead, it requires the UTF-16 surrogate pair in order to return a supplementary character:

String.fromCharCode(0xd83c, 0xdf03); // Code Point U+1F303 "Night with
String.fromCharCode(55356, 57091); // Stars" === "\uD83C\uDF03"

另一方面，String.fromCodePoint() 可以通过指定代码点（相当于 UTF-32 代码单元）返回 4 字节补充字符以及更常见的 2 字节 BMP 字符：

¥String.fromCodePoint(), on the other hand, can return 4-byte supplementary characters, as well as the more common 2-byte BMP characters, by specifying their code point (which is equivalent to the UTF-32 code unit):

String.fromCodePoint(0x1f303); // or 127747 in decimal

¥See also

• core-js 中 String.fromCodePoint 的 Polyfill
• String.fromCharCode()
• String.prototype.charAt()
• String.prototype.codePointAt()
• String.prototype.charCodeAt()