Complete "longest common ..." examples (#100)

* no else return

* fix var ref

* fix importing/requiring dependencies

* complete longest common examples

09_dynamic_programming/javascript/examples/base.js

@@ -1,7 +1,7 @@
-export default function initialize_matrix(rows, cols){
-    let matrix = [];
-    for (let i = 0; i < rows.length; i++){
-        matrix.push(Array(cols.length).fill(0));
-    }
-    return matrix;
-}
+module.exports = function initialize_matrix(rows, cols) {
+  let matrix = [];
+  for (let i = 0; i < rows.length; i++) {
+    matrix.push(Array(cols.length).fill(0));
+  }
+  return matrix;
+};