🔰surrogate pair

two-code-unit character.

JS ⟩ value ⟩ primitive ⟩ String ⟩ Unicode ⟩ encoding ⟩ UTF-16 ⟩ surrogate pair

code points beyond the basic multilingual plane (also called astral code points) that are transformed into two UTF-16 code units.

• two parts of the pair must be in 0xD800 ~ 0xDFFF. (2^11 = 0x800)

  • high-surrogate code unit : 0xD800 ~ 0xDBFF. (2^10 = 0x400)

  • low-surrogate code unit : 0xDC00 ~ 0xDFFF. (2^10 = 0x400)

• these code units (called "lone surrogates") are not used to encode single-code-unit characters.

🗺️ 圖表

📗

• Eloquent JavaScript ⟩ Strings & Character Codes

📘 手冊

• UTF-16 characters, code points, grapheme clusters

• String.prototype ⟩

  • .charCodeAt()

  • .codePointAt()

• String ⟩

  • .fromCodePoint()

  • .fromCharCode()