Isomorphisms and round trip data transformations

Author: kumarbhot

26.introduction-isomorphism.js

@@ -0,0 +1,37 @@
+const { Right, Left } = require('./either');
+
+// from(to(x)) === x
+// to(from(x)) === x
+// String ~ [Char]
+const Iso = (to, from) => ({ to, from });
+
+const chars = Iso(s => s.split(''), c => c.join(''));
+
+const helloWorld = 'hello world';
+const arrHelloWorld = [ 'h', 'e', 'l', 'l', 'o', 'w', 'o', 'r', 'l', 'd' ];
+
+const res1 = chars.from(chars.to(helloWorld));
+const res2 = chars.to(chars.from(arrHelloWorld));
+
+console.log(res1, helloWorld);
+console.log(res2, arrHelloWorld);
+
+const truncate = str => chars.from(chars.to(str).slice(0, 3)).concat('...');
+
+const res3 = truncate(helloWorld);
+
+console.log(res3, 'hel...');
+
+// [a] ~ Either || null || a
+const singleton = Iso(
+  e => e.fold(() => [], x => [x]),
+  ([x]) => x ? Right(x) : Left()
+);
+
+const filterEither = (e, pred) => singleton.from(singleton.to(e).filter(pred));
+
+const res4 = filterEither(
+  Right('hello'),
+  x => x.match(/h/ig)).map(x => x.toUpperCase(x));
+
+console.log(res4);

README.md

@@ -27,6 +27,7 @@
 23. [Maintaining structure whilst asyncing](23.maintaining-structure-whilst-asyncing.js)
 24. [Principled type conversions with Natural Transformations](24.natural-transformations.js)
 25. [Apply Natural Transformations in everyday work](25.everyday-natural-transformations.js)
+26. [Isomorphisms and round trip data transformations](26.introduction-isomorphism.js)
 
 ## How to run