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input = document.getElementById("rot13-input")
output = document.getElementById("rot13-output")
shift_range = document.getElementById("rot13-shift")
shift_output = document.getElementById("rot13-shift-output")
const letters_low = [
"a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m",
"n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"
]
const letters_up = letters_low.map(c => c.toUpperCase())
function rotate(text, shift) {
return text.split("").map(c => {
if (/[a-zA-Z]/.test(c)) {
letters = /[a-z]/.test(c) ? letters_low : letters_up
return letters[(letters.indexOf(c) + shift) % 26]
}
return c
}).join("")
}
function update() {
output.value = rotate(input.value, Number(shift_range.value))
shift_output.textContent = shift_range.value
}
input.addEventListener("keyup", update)
shift_range.addEventListener("input", update)
update()
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