// In the future, I would like to do something more sensible to typeset complex units, but for now this will do function units(u, args) { const { base, prefix, siPrefixes } = { base: null, prefix: 0, siPrefixes: false, ...args }; class QuantityWithUnits extends Number { toString() {} } const fn = function (num, dp = null) { // parseFloat(toFixed) gets rid of trailing zeros const val = dp === null ? num : parseFloat(num.toFixed(dp)); const [int, frac] = val.toString().split("."); function* sp_right(str) { for (let i = 0; i < str.length; i++) { yield str[i]; if ( (str.length - 1 - i) % 3 == 0 && i < str.length - 1 && str[i] != "-" && str[i] != "+" ) { yield "\u00A0"; } } } let str = [...sp_right(int)].join("").replace("-", "—"); if (typeof frac !== "undefined") { str = [str, frac].join(thousands_separator); } let markup = u ? html`${str} ${u}` : html`${str}`; markup.value = num; markup.units = u; return markup; }; if (siPrefixes) { fn.prefix = prefix; fn.prefixed = (p) => base !== null ? base.prefixed(prefix + p) : units(`${si_prefixes[p]}${u}`, { base: fn, prefix: p, siPrefixes: true }); fn.readable = function (value, dp = null) { // Express the value in the best prefix for it const bestPrefix = Math.floor(Math.log(value) / Math.log(1000)) * 3; let bestValue = value / Math.pow(10, bestPrefix); return fn.prefixed(bestPrefix)(bestValue, dp); }; } fn.unit = u; return fn; }

Purpose-built for displays of data