init

lib/extractor.ts

@@ -0,0 +1,21 @@
+
+export class Extractor<O> {
+    private extract: (text: string) => O | null;
+
+    public constructor(extract: (text: string) => O | null) {
+        this.extract = extract;
+    }
+
+    public get(text: string) {
+        return this.extract(text);
+    }
+
+    public or<T>(other: Extractor<T>) {
+        const this_extract = this.extract;
+        return new Extractor(text => {
+            const r1 = this_extract(text);
+            if (r1 !== null) return r1;
+            else return other.extract(text);
+        });
+    }
+}