Refactoring

src/functions/map.ts

@@ -0,0 +1,29 @@
+import { Transform } from "stream";
+import { TransformOptions } from "./baseDefinitions";
+/**
+ * Return a ReadWrite stream that maps streamed chunks
+ * @param mapper Mapper function, mapping each (chunk, encoding) to a new chunk (or a promise of such)
+ * @param options
+ * @param options.readableObjectMode Whether this stream should behave as a readable stream of objects
+ * @param options.writableObjectMode Whether this stream should behave as a writable stream of objects
+ */
+export function map<T, R>(
+    mapper: (chunk: T, encoding: string) => R,
+    options: TransformOptions = {
+        readableObjectMode: true,
+        writableObjectMode: true,
+    },
+): Transform {
+    return new Transform({
+        ...options,
+        async transform(chunk: T, encoding, callback) {
+            try {
+                const mapped = await mapper(chunk, encoding);
+                this.push(mapped);
+                callback();
+            } catch (err) {
+                callback(err);
+            }
+        },
+    });
+}