From 60b404f4d98c26f33e1b5a5b182a4a78f9a2af03 Mon Sep 17 00:00:00 2001
From: Ardis Lu <ardisglu@gmail.com>
Date: Sat, 5 Jul 2025 19:14:40 -0700
Subject: [PATCH] Support ArrayLike outputs

Could be useful for chained transformations using DOM APIs, e.g. passing through the NodeList object.
---
 src/core.js       | 15 ++++++++++-----
 test/core.test.js | 11 +++++++++++
 2 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/src/core.js b/src/core.js
index 81e13ff..d2bcc6a 100644
--- a/src/core.js
+++ b/src/core.js
@@ -196,7 +196,7 @@ export class CSVReader extends ReadableStream {
 
 /**
  * A row or rows of output CSV data, or `null` to not output anything.
- * @typedef {Array<Array<any>>|Array<any>|string|null} TransformationOutput
+ * @typedef {Array<Array<any>>|Array<any>|ArrayLike<any>|string|null} TransformationOutput
  */
 
 /**
@@ -402,11 +402,16 @@ export class CSVTransformer extends TransformStream {
     else if (this.#rawOutput || typeof row === 'string') {
       controller.enqueue(row);
     }
-    else if (Array.isArray(row) && Array.isArray(row[0])) { // Multiple rows returned, enqueue each row separately
-      row.forEach(r => controller.enqueue(JSON.stringify(r)));
+    else if (Array.isArray(row)) {
+      if (Array.isArray(row[0])) { // Multiple rows returned, enqueue each row separately
+        row.forEach(r => controller.enqueue(JSON.stringify(r)));
+      }
+      else { // One row returned
+        controller.enqueue(JSON.stringify(row));
+      }
     }
-    else {
-      controller.enqueue(JSON.stringify(row));
+    else { // Assume ArrayLike output
+      controller.enqueue(JSON.stringify(Array.from(row)));
     }
   }
 
diff --git a/test/core.test.js b/test/core.test.js
index 1c4918e..3e0180e 100644
--- a/test/core.test.js
+++ b/test/core.test.js
@@ -327,6 +327,17 @@ suite('CSVTransformer', { concurrency: true }, () => {
         ['abc', 'def']
       ]));
   });
+  test('handles ArrayLike outputs', { concurrency: true }, async () => {
+    await createCSVMockStream([
+      ['columnA', 'columnB'],
+      ['a', 'b']
+    ])
+      .pipeThrough(new CSVTransformer(() => ({ length: 2, 0: 'a2', 1: 'b2' })))
+      .pipeTo(csvStreamEqualWritable([
+        ['columnA', 'columnB'],
+        ['a2', 'b2']
+      ]));
+  });
   test('consumes input row without output row when null is returned', { concurrency: true }, async () => {
     await createCSVMockStream([
       ['columnA', 'columnB'],
-- 
2.47.3