Building a Unicode Text Transformer with Pure Character Maps

I built Unicode Text Tools , a free site with a bunch of text converters — superscript, subscript, bubble/circled text, upside-down text, small caps, and more. Type something, get it transformed, copy it out. The whole engine is one dependency-free JS file built entirely from character mapping tables . No AI, no server, no libraries. Here's why that's the right architecture for this class of tool, and how the trickier conversions work. The core idea: it's all just lookup tables Every conversion on the site is a function that maps each input character to a Unicode character (or does a small transform). The simplest cases are pure dictionaries: // Superscript (full a-z, 0-9) var SUP = { a : ' ᵃ ' , b : ' ᵇ ' , c : ' ᶜ ' , d : ' ᵈ ' , e : ' ᵉ ' , f : ' ᶠ ' , g : ' ᵍ ' , h : ' ʰ ' , i : ' ⁱ ' , j : ' ʲ ' , k : ' ᵏ ' , l : ' ˡ ' , m : ' ᵐ ' , n : ' ⁿ ' , o : ' ᵒ ' , p : ' ᵖ ' , q : ' ᵠ ' , r : ' ʳ ' , s : ' ˢ ' , t : ' ᵗ ' , u : ' ᵘ ' , v : ' ᵛ ' , w : ' ʷ ' , x : ' ˣ ' , y : ' ʸ ' , z : ' ᶻ ' , ' 0 ' : ' ⁰ ' , ' 1 ' : ' ¹ ' , ' 2 ' : ' ² ' , ' 3 ' : ' ³ ' , ' 4 ' : ' ⁴ ' , ' 5 ' : ' ⁵ ' , ' 6 ' : ' ⁶ ' , ' 7 ' : ' ⁷ ' , ' 8 ' : ' ⁸ ' , ' 9 ' : ' ⁹ ' , ' + ' : ' ⁺ ' , ' - ' : ' ⁻ ' , ' = ' : ' ⁼ ' , ' ( ' : ' ⁽ ' , ' ) ' : ' ⁾ ' }; The transform itself is trivial — walk the string, look up each char, append the mapped value (or the original char if unmapped). The work is in the tables: knowing which Unicode blocks exist, what's 1:1 reversible, and what's incomplete. The Unicode reality check Here's the thing nobody tells you about Unicode text transformation: the blocks are inconsistent. Superscript : complete for a-z and 0-9 — fully reversible. Subscript : incomplete — there's no subscript b , c , d , f , g , q , w , y , z . If you map an input with those letters, you have to decide what to do with them. Small caps : x has no small-cap form ( ꞯ is the closest, but it's a different character and looks wrong). j is a problem too — the Unicode small-cap ᴊ collides visually