What does the "code unit value" mean in ECMA-262 (JavaScript 5 edition)?

I开发者_开发问答'm watching ECMA-262 (JavaScript 5 edition) and cannot understand what is "code unit value"?

Can anyone tell me?

Thank you very much!

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A JavaScript string is a sequence of unsigned 16-bit integers, also known as code units.

A code point is how the Unicode standard represents symbols and non-symbols. Code points are represented as a four-to-six digit hexadecimal number, typically prefixed with U+, e.g. U+0061 LATIN SMALL LETTER A.

The difference is that what can be part of a code unit depends on the character encoding that is used. A code point however, is merely the concept of a “character” that can then potentially be encoded using UTF-8, for example.

For more information, read chapter 2 of the Unicode spec, especially 2.4 Code points and characters.