javascript - JavaScript 字符串如何是一组 "elements"16 位无符号整数值？

Question

来自MDN

JavaScript's String type is used to represent textual data. It is a set of "elements" of 16-bit unsigned integer values. Each element in the String occupies a position in the String. The first element is at index 0, the next at index 1, and so on. The length of a String is the number of elements in it. You can create strings using string literals or string objects.

JavaScript String 类型为何是一组 16 位无符号整数值的“元素”，为什么不是 8 位无符号整数值？

Answer 1

查看full spec text这里有帮助:

The String type is the set of all ordered sequences of zero or more 16-bit unsigned integer values (“elements”) up to a maximum length of 2⁵³-1 elements. The String type is generally used to represent textual data in a running ECMAScript program, in which case each element in the String is treated as a UTF-16 code unit value.

类似的可以在ES5.1 spec中找到.

为什么不是 8 位无符号整数值？如果使用 UTF-8，这同样是可能的。但它并没有完成，现在就是这样。