文档：https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/fromCharCode
String.fromCharCode()
The String.fromCharCode() static method returns a string created from the specified sequence of UTF-16 code units.
Example
console.log(String.fromCharCode(189, 43, 190, 61));
// Expected output: "½+¾="
Syntax
String.fromCharCode()
String.fromCharCode(num1)
String.fromCharCode(num1, num2)
String.fromCharCode(num1, num2, /* …, */ numN)
Parameters
num1, …, numN
A number between 0 and 65535 (0xFFFF) representing a UTF-16 code unit. Numbers greater than 0xFFFF are truncated to the last 16 bits. No validity checks are performed.
Return value
A string of length N consisting of the N specified UTF-16 code units.