diff --git a/lib/_debugger.js b/lib/_debugger.js
index 99b55a8b50e07d..be1b0f62daf151 100644
--- a/lib/_debugger.js
+++ b/lib/_debugger.js
@@ -1363,7 +1363,7 @@ Interface.prototype.setBreakpoint = function(script, line,
       for (var id in scripts) {
         if (scripts[id] &&
             scripts[id].name &&
-            scripts[id].name.indexOf(script) !== -1) {
+            scripts[id].name.includes(script)) {
           if (scriptId) {
             ambiguous = true;
           }
@@ -1441,7 +1441,7 @@ Interface.prototype.clearBreakpoint = function(script, line) {
   this.client.breakpoints.some(function(bp, i) {
     if (bp.scriptId === script ||
         bp.scriptReq === script ||
-        (bp.script && bp.script.indexOf(script) !== -1)) {
+        (bp.script && bp.script.includes(script))) {
       if (!util.isUndefined(index)) {
         ambiguous = true;
       }
@@ -1459,7 +1459,7 @@ Interface.prototype.clearBreakpoint = function(script, line) {
     for (var id in scripts) {
       if (scripts[id] &&
           scripts[id].name &&
-          scripts[id].name.indexOf(script) !== -1) {
+          scripts[id].name.includes(script)) {
         if (scriptId) {
           ambiguous = true;
         }
diff --git a/lib/dns.js b/lib/dns.js
index 0a6e84a435da02..84255119b72035 100644
--- a/lib/dns.js
+++ b/lib/dns.js
@@ -77,7 +77,7 @@ function onlookup(err, addresses) {
   if (this.family) {
     this.callback(null, addresses[0], this.family);
   } else {
-    this.callback(null, addresses[0], addresses[0].indexOf(':') >= 0 ? 6 : 4);
+    this.callback(null, addresses[0], addresses[0].includes(':') ? 6 : 4);
   }
 }
 
diff --git a/lib/fs.js b/lib/fs.js
index 2d7a038e156a66..211add74d8101c 100644
--- a/lib/fs.js
+++ b/lib/fs.js
@@ -84,7 +84,7 @@ function assertEncoding(encoding) {
 }
 
 function nullCheck(path, callback) {
-  if (('' + path).indexOf('\u0000') !== -1) {
+  if (('' + path).includes('\u0000')) {
     var er = new Error('Path must be a string without null bytes.');
     if (!callback)
       throw er;
diff --git a/lib/module.js b/lib/module.js
index 0a4195cf7b7504..2ba04b2fb48092 100644
--- a/lib/module.js
+++ b/lib/module.js
@@ -238,7 +238,7 @@ Module._resolveLookupPaths = function(request, parent) {
 
   // make sure require('./path') and require('path') get distinct ids, even
   // when called from the toplevel js file
-  if (parentIdPath === '.' && id.indexOf('/') === -1) {
+  if (parentIdPath === '.' && !id.includes('/')) {
     id = './' + id;
   }
 
diff --git a/lib/url.js b/lib/url.js
index abe66acfca983b..7ba812b82f2553 100644
--- a/lib/url.js
+++ b/lib/url.js
@@ -298,7 +298,7 @@ Url.prototype.parse = function(url, parseQueryString, slashesDenoteHost) {
     // need to be.
     for (var i = 0, l = autoEscape.length; i < l; i++) {
       var ae = autoEscape[i];
-      if (rest.indexOf(ae) === -1)
+      if (!rest.includes(ae))
         continue;
       var esc = encodeURIComponent(ae);
       if (esc === ae) {
@@ -375,7 +375,7 @@ Url.prototype.format = function() {
   if (this.host) {
     host = auth + this.host;
   } else if (this.hostname) {
-    host = auth + (this.hostname.indexOf(':') === -1 ?
+    host = auth + (!this.hostname.includes(':') ?
         this.hostname :
         '[' + this.hostname + ']');
     if (this.port) {
diff --git a/lib/util.js b/lib/util.js
index 891a376c2d955c..7bbff7f3b2bf26 100644
--- a/lib/util.js
+++ b/lib/util.js
@@ -439,7 +439,7 @@ function formatProperty(ctx, value, recurseTimes, visibleKeys, key, array) {
       } else {
         str = formatValue(ctx, desc.value, recurseTimes - 1);
       }
-      if (str.indexOf('\n') > -1) {
+      if (str.includes('\n')) {
         if (array) {
           str = str.split('\n').map(function(line) {
             return '  ' + line;