From bc1099b05940a9456c570b070acbc28d0be1e67a Mon Sep 17 00:00:00 2001
From: Ardis Lu <ardisglu@gmail.com>
Date: Wed, 8 Jan 2025 21:44:24 -0800
Subject: [PATCH] Add example for returning null in transformation

---
 examples/data/ex5-in.csv  | 10 ++++++++++
 examples/data/ex5-out.csv |  5 +++++
 examples/ex5.js           | 29 +++++++++++++++++++++++++++++
 3 files changed, 44 insertions(+)
 create mode 100644 examples/data/ex5-in.csv
 create mode 100644 examples/data/ex5-out.csv
 create mode 100644 examples/ex5.js

diff --git a/examples/data/ex5-in.csv b/examples/data/ex5-in.csv
new file mode 100644
index 0000000..9042246
--- /dev/null
+++ b/examples/data/ex5-in.csv
@@ -0,0 +1,10 @@
+ABC System Report
+ID# XXX-123
+2025-01-08
+,,
+,,
+Name,Value_1,Value_2
+A,1111,11
+B,2222,22
+C,3333,33
+D,4444,44
diff --git a/examples/data/ex5-out.csv b/examples/data/ex5-out.csv
new file mode 100644
index 0000000..a874060
--- /dev/null
+++ b/examples/data/ex5-out.csv
@@ -0,0 +1,5 @@
+Report,ID,Date,Name,Value_1,Value_2
+ABC System Report,XXX-123,2025-01-08,A,1111,11
+ABC System Report,XXX-123,2025-01-08,B,2222,22
+ABC System Report,XXX-123,2025-01-08,C,3333,33
+ABC System Report,XXX-123,2025-01-08,D,4444,44
diff --git a/examples/ex5.js b/examples/ex5.js
new file mode 100644
index 0000000..e08db19
--- /dev/null
+++ b/examples/ex5.js
@@ -0,0 +1,29 @@
+// ## Example 5: Handling an irregularly-shaped CSV file
+// 
+// `createCSVReadableStream` can parse CSVs that have rows with a mismatching number of columns, for example CSVs
+// with informational file headers. This information can be handled as required in the transformation function.
+//
+// Return `null` in the transformation function to consume an input row without emitting an output row.
+
+import { createCSVReadableStream, createCSVTransformStream, createCSVWritableStream } from '../src/index.js';
+
+let i = 0;
+let report, id, date;
+function parse(row) {
+  // Special logic for the first six rows of the CSV
+  switch (i++) {
+    case 0: report = row[0]; return null;
+    case 1: id = row[0].split(' ')[1]; return null;
+    case 2: date = row[0]; return null;
+    case 3: return null;
+    case 4: return null;
+    case 5: return ['Report', 'ID', 'Date', 'Name', 'Value_1', 'Value_2'];
+  }
+
+  // Normal logic for the rest of the CSV
+  return [report, id, date, ...row];
+}
+
+createCSVReadableStream('./data/ex5-in.csv')
+  .pipeThrough(createCSVTransformStream(parse, { includeHeaders: true }))
+  .pipeTo(createCSVWritableStream('./data/ex5-out.csv'));
\ No newline at end of file
-- 
2.47.3