Figure out what casing various Unicode code points are mapped to by javascript

index.js

// This program only mapps the Latin-1 and Latin-1 Supplement code range but can be extended to support anything

function mkInterval(a) {
  return [a[0], a[1], a[1] - a[0]]
}

function adj(a, b) {
  return (a[0] + 1 == b[0])
    && (a[1] + 1 == b[1])
    && (a[2] == b[2])
}

let map = []
for (let i = 0x20; i <= 0xFF; i++) { // basic latin and latin-1 supplement
  const a = String.fromCharCode(i)
  const b = a.toLowerCase().charCodeAt(0)
  if (i !== b) {
    map.push(mkInterval([i, b]))
  }
}

// Find all continuous intervals
const cont = []

let a = map.shift()
cont.push(a)
for (; ;) {
  const b = map.shift()
  if (!b) {
    break
  }
  if (adj(a, b)) {
    const c = cont.pop()
    c[1] = b[0]
    cont.push(c)
  } else {
    cont.push(b)
  }
  a = b
}

//DEBUG
// cont.forEach((c) => {
//   const xs = []
//   for (let i = c[0]; i < c[1]; i++) {
//     xs.push(`${String.fromCharCode(i)} -> ${String.fromCharCode(i + c[2])}`)
//   }
//   console.log(xs.join(', '))
// })

console.log(cont)