1 files changed, 31 insertions, 0 deletions
diff --git a/utils/rot13/script.js b/utils/rot13/script.js
new file mode 100644
index 0000000..efa408b
--- /dev/null
+++ b/utils/rot13/script.js
@@ -0,0 +1,31 @@
+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()