New: Adds codemod from arrow to fn declaration

codemods/to-function-declaration.js

@@ -0,0 +1,58 @@
+// @ts-check
+// @ts-ignore
+module.exports = transform;
+module.exports.title = 'To function declaration';
+module.exports.description =
+  'Changes from const foo = (a, b) => a + b to function foo (a, b) { return a + b; }';
+
+function transform(file, api, options) {
+  const j = api.jscodeshift;
+
+  const printOptions = options.printOptions || { quote: 'single' };
+  const root = j(file.source);
+
+  function getBodyStatement(fn) {
+    const inner = fn.body;
+    const comments = (fn.body.comments || []).concat(inner.comments || []);
+    if (j.Expression.check(fn.body)) {
+      inner.comments = (inner.comments || []).concat(comments);
+      return j.blockStatement([j.returnStatement(inner)]);
+    }
+    return fn.body;
+  }
+
+  function createFunctionExpression(fn, id) {
+    const func = j.functionDeclaration(id, fn.params, getBodyStatement(fn));
+    func.comments = fn.comments;
+    return func;
+  }
+
+  const replacedCallbacks =
+    root
+      .find(j.VariableDeclaration)
+      .filter(path => {
+        return path.value.declarations.every(f => j.ArrowFunctionExpression.check(f.init));
+      })
+      .forEach(function(pp) {
+        j(pp).replaceWith(
+          j(pp.value.declarations)
+            .filter(path => {
+              const fn = path.value.init;
+              const noThis =
+                j(fn)
+                  .find(j.ThisExpression)
+                  .size() == 0;
+
+              return j.ArrowFunctionExpression.check(fn) && noThis;
+            })
+            .nodes()
+            .map(decl => {
+              console.log(decl.init);
+              return createFunctionExpression(decl.init, decl.id);
+            })
+        );
+      })
+      .size() > 0;
+
+  return replacedCallbacks ? root.toSource(printOptions) : null;
+}