diff --git a/src/graph.js b/src/graph.js
index a921380..3452816 100644
--- a/src/graph.js
+++ b/src/graph.js
@@ -24,7 +24,7 @@
 
 const fs = require('fs');
 const graph = (path) => {
-  return fs.readFileSync(path, "utf-8");
+  return fs.readFileSync(path, 'utf-8');
 };
 
 module.exports = graph;
diff --git a/src/index.js b/src/index.js
index 5052188..973d4e0 100644
--- a/src/index.js
+++ b/src/index.js
@@ -31,8 +31,8 @@ const path = require('path');
 const filed = require('./tokens.js');
 const query = require('./graph.js');
 const pkg = require('../package.json');
-let fs = require('fs');
-const nestedProp = require("./nested-prop.js");
+const fs = require('fs');
+const nestedProp = require('./nested-prop.js');
 
 console.log(`Running ghminer@${pkg.version}`);
 const argv = minimist(process.argv.slice(2));
@@ -43,8 +43,8 @@ const startDate = argv.start || '2008-01-01';
 const endDate = argv.end || now;
 const dateType = argv.date || 'created';
 const print = argv.json || false;
-const gpath = argv.graphql || "ghminer.graphql";
-const schema = argv.schema || "ghminer.json";
+const gpath = argv.graphql || 'ghminer.graphql';
+const schema = argv.schema || 'ghminer.json';
 
 let tokens;
 if (argv.tokens) {
@@ -231,7 +231,7 @@ async function fetchAllResults() {
  * @param {Object} json Json objects
  */
 function writeFiles(json) {
-  let format = JSON.parse(fs.readFileSync(schema, "utf-8"));
+  const format = JSON.parse(fs.readFileSync(schema, 'utf-8'));
   const formattedResults = json.map((result) => {
     const data = {};
     for (const [key, path] of Object.entries(format)) {
diff --git a/src/nested-prop.js b/src/nested-prop.js
index 8df5b5d..34963a8 100644
--- a/src/nested-prop.js
+++ b/src/nested-prop.js
@@ -35,9 +35,13 @@ const nestedProp = (obj, path) => {
         return acc[arrayKey] && Array.isArray(acc[arrayKey]) ? acc[arrayKey] : [];
       }
     }
-    return Array.isArray(acc)
-      ? acc.map(item => item[key] !== undefined ? item[key] : null)
-      : acc[key] !== undefined ? acc[key] : null;
+    if (Array.isArray(acc)) {
+      return acc.map((item) => item[key] !== undefined ? item[key] : null);
+    } else if (acc[key] !== undefined) {
+      return acc[key];
+    } else {
+      return null;
+    }
   }, obj);
 };
 
diff --git a/test/nested-prop.test.js b/test/nested-prop.test.js
index 4f6a232..b261055 100644
--- a/test/nested-prop.test.js
+++ b/test/nested-prop.test.js
@@ -24,12 +24,12 @@
 const assert = require('assert');
 const nested = require('../src/nested-prop');
 
-describe('Test case for nested-prop.js', function () {
-  it('returns prop', function () {
+describe('Test case for nested-prop.js', function() {
+  it('returns prop', function() {
     const obj = {
-      test: "aaa"
+      test: 'aaa'
     };
-    const prop = nested(obj, "test")
+    const prop = nested(obj, 'test')
     const expected = 'aaa';
     assert.equal(
       prop,
@@ -37,13 +37,13 @@ describe('Test case for nested-prop.js', function () {
       `parsed ${prop} does not match with expected ${expected}`
     );
   });
-  it('returns nested prop', function () {
+  it('returns nested prop', function() {
     const obj = {
       test: {
-        aaa: "bbb"
+        aaa: 'bbb'
       }
     };
-    const prop = nested(obj, "test.aaa")
+    const prop = nested(obj, 'test.aaa')
     const expected = 'bbb';
     assert.equal(
       prop,
@@ -51,7 +51,7 @@ describe('Test case for nested-prop.js', function () {
       `parsed ${prop} does not match with expected ${expected}`
     );
   });
-  it('returns first nested prop from array', function () {
+  it('returns first nested prop from array', function() {
     const obj = {
       defaultBranchRef: {
         target: {
@@ -59,7 +59,7 @@ describe('Test case for nested-prop.js', function () {
             edges: [
               {
                 node: {
-                  committedDate: "2024-10-01"
+                  committedDate: '2024-10-01'
                 }
               }
             ]
@@ -69,7 +69,7 @@ describe('Test case for nested-prop.js', function () {
     };
     const prop = nested(
       obj,
-      "defaultBranchRef.target.history.edges[0].node.committedDate"
+      'defaultBranchRef.target.history.edges[0].node.committedDate'
     );
     const expected = '2024-10-01';
     assert.equal(
@@ -78,28 +78,28 @@ describe('Test case for nested-prop.js', function () {
       `parsed ${prop} does not match with expected ${expected}`
     );
   });
-  it('returns array of nested props', function () {
+  it('returns array of nested props', function() {
     const obj = {
       repositoryTopics: {
         edges: [
           {
             node: {
               topic: {
-                name: "java"
+                name: 'java'
               }
             }
           },
           {
             node: {
               topic: {
-                name: "jvm"
+                name: 'jvm'
               }
             }
           },
           {
             node: {
               topic: {
-                name: "compilers"
+                name: 'compilers'
               }
             }
           }
@@ -108,7 +108,7 @@ describe('Test case for nested-prop.js', function () {
     };
     const prop = nested(
       obj,
-      "repositoryTopics.edges[].node.topic.name"
+      'repositoryTopics.edges[].node.topic.name'
     );
     const expected = 'java,jvm,compilers';
     assert.equal(