CJK and Latin spacing

Adds a space where Chinese or Japanese text meets Latin letters or numbers, e.g. 用Python写5个脚本 becomes 用 Python 写 5 个脚本.

Text

Numbers too Common symbols (% + # @ $)

Result

Rules

CJK means Han characters, hiragana, katakana and the iteration mark 々. Hangul is left alone, since Korean already uses spaces between words.
A space is added between a CJK character and an adjacent Latin letter (including accented ones), and optionally a digit.
With symbols on, %, + and # count as part of the Latin side when they follow a letter or digit and come before CJK (50%的, C++写), and #, @ and $ when they come after CJK and precede a letter or digit (见#12, 花$5). A symbol between two CJK characters, as in 话题#标签, is left alone.
Nothing is added next to full-width punctuation such as ，。（）, and existing spaces are kept as they are.

Runs in your browser; nothing is uploaded.