diff --git a/javascript/rna-transcription/rna-transcription.js b/javascript/rna-transcription/rna-transcription.js
new file mode 100644
index 0000000..e0d7e99
--- /dev/null
+++ b/javascript/rna-transcription/rna-transcription.js
@@ -0,0 +1,18 @@
+const changer = (char) => {
+  switch (char) {
+    case 'G':
+      return 'C';
+    case 'C':
+      return 'G';
+    case 'T':
+      return 'A';
+    case 'A':
+      return 'U';
+    default:
+      throw new Error('Invalid input DNA.');
+  }
+};
+
+const toRna = dna => dna.split('').map(changer).join('');
+
+export { toRna };
diff --git a/javascript/rna-transcription/rna-transcription.spec.js b/javascript/rna-transcription/rna-transcription.spec.js
new file mode 100644
index 0000000..2a5b8b9
--- /dev/null
+++ b/javascript/rna-transcription/rna-transcription.spec.js
@@ -0,0 +1,40 @@
+import { toRna } from './rna-transcription';
+
+describe('Transcriptor', () => {
+  test('empty rna sequence', () => {
+    expect(toRna('')).toEqual('');
+  });
+
+  test('transcribes cytosine to guanine', () => {
+    expect(toRna('C')).toEqual('G');
+  });
+
+  test('transcribes guanine to cytosine', () => {
+    expect(toRna('G')).toEqual('C');
+  });
+
+  test('transcribes adenine to uracil', () => {
+    expect(toRna('A')).toEqual('U');
+  });
+
+  test('transcribes thymine to adenine', () => {
+    expect(toRna('T')).toEqual('A');
+  });
+
+  test('transcribes all dna nucleotides to their rna complements', () => {
+    expect(toRna('ACGTGGTCTTAA'))
+      .toEqual('UGCACCAGAAUU');
+  });
+
+  test('correctly handles invalid input', () => {
+    expect(() => toRna('U')).toThrow(new Error('Invalid input DNA.'));
+  });
+
+  test('correctly handles completely invalid input', () => {
+    expect(() => toRna('XXX')).toThrow(new Error('Invalid input DNA.'));
+  });
+
+  test('correctly handles partially invalid input', () => {
+    expect(() => toRna('ACGTXXXCTTAA')).toThrow(new Error('Invalid input DNA.'));
+  });
+});