feat: Added 50 Pow(x,n) for nodejs

- feat: Added using recursion for permuatation problem example in nodejs

rec-permute/nodejs/index.js

@@ -0,0 +1,18 @@
+const RecPermute = (soFar, rest) => {
+  if (rest.length === 0) {
+    console.log('result', soFar);
+    console.log('\n\n');
+  } else {
+    for (let i = 0; i < rest.length; i++) {
+      const remaining = rest.substring(0,i) + rest.substring(i+1);
+      console.log('r', remaining) 
+      console.log('R', rest);
+      console.log('SF', soFar);
+      console.log('------');
+      RecPermute(soFar + rest[i], remaining);
+    }
+  }
+};
+
+x = 'abc';
+RecPermute('', x);