alphabet: add back support for array of strings

index.ts

@@ -52,11 +52,14 @@ function chain<T extends Chain & AsChain<T>>(...args: T): Coder<Input<First<T>>,
 }
 
 /**
- * Encodes integer radix representation to array of strings using alphabet and back
+ * Encodes integer radix representation to array of strings using alphabet and back.
+ * Could also be array of strings.
  */
 function alphabet(letters: string): Coder<number[], string[]> {
-  if (typeof letters !== 'string') throw new Error('invalid alphabet');
-  const indexes = Object.fromEntries(letters.split('').map((l, i) => [l, i]));
+  const lettersArr = typeof letters === 'string' ? letters.split('') : letters;
+  if (!isArrayOf('string', lettersArr))
+    throw new Error('alphabet expects string or array of strings');
+  const indexes = Object.fromEntries(lettersArr.map((l, i) => [l, i]));
   return {
     encode: (digits: number[]) => {
       if (!isArrayOf('number', digits))

test/bases.test.js

@@ -187,6 +187,10 @@ should('utils: radix', () => {
 
 should('utils: alphabet', () => {
   const a = utils.alphabet('12345');
+  const ab = utils.alphabet(['11', '2', '3', '4', '5']);
+  assert.deepStrictEqual(a.encode([1]), ['2']);
+  assert.deepStrictEqual(ab.encode([0]), ['11']);
+  assert.deepStrictEqual(a.encode([2]), ab.encode([2]));
   assert.throws(() => a.encode([1, 2, true, 3]));
   assert.throws(() => a.decode(['1', 2, true]));
   assert.throws(() => a.decode(['1', 2]));