querystring: lazy loaded

PR-URL: #20567
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>

lib/internal/url.js

@@ -27,7 +27,9 @@ const {
   CHAR_LOWERCASE_A,
   CHAR_LOWERCASE_Z,
 } = require('internal/constants');
-const querystring = require('querystring');
+
+// Lazy loaded for startup performance.
+let querystring;
 
 const { platform } = process;
 const isWindows = platform === 'win32';
@@ -771,8 +773,10 @@ function parseParams(qs) {
       } else if (encodeCheck > 0) {
         // eslint-disable-next-line no-extra-boolean-cast
         if (!!isHexTable[code]) {
-          if (++encodeCheck === 3)
+          if (++encodeCheck === 3) {
+            querystring = require('querystring');
             encoded = true;
+          }
         } else {
           encodeCheck = 0;
         }

lib/url.js

@@ -94,7 +94,6 @@ const slashedProtocol = {
   'file': true,
   'file:': true
 };
-const querystring = require('querystring');
 const {
   CHAR_SPACE,
   CHAR_TAB,
@@ -133,6 +132,9 @@ const {
   CHAR_AT,
 } = require('internal/constants');
 
+// Lazy loaded for startup performance.
+let querystring;
+
 function urlParse(url, parseQueryString, slashesDenoteHost) {
   if (url instanceof Url) return url;
 
@@ -233,6 +235,7 @@ Url.prototype.parse = function parse(url, parseQueryString, slashesDenoteHost) {
       if (simplePath[2]) {
         this.search = simplePath[2];
         if (parseQueryString) {
+          if (querystring === undefined) querystring = require('querystring');
           this.query = querystring.parse(this.search.slice(1));
         } else {
           this.query = this.search.slice(1);
@@ -422,6 +425,7 @@ Url.prototype.parse = function parse(url, parseQueryString, slashesDenoteHost) {
       this.query = rest.slice(questionIdx + 1, hashIdx);
     }
     if (parseQueryString) {
+      if (querystring === undefined) querystring = require('querystring');
       this.query = querystring.parse(this.query);
     }
   } else if (parseQueryString) {
@@ -584,8 +588,10 @@ Url.prototype.format = function format() {
     }
   }
 
-  if (this.query !== null && typeof this.query === 'object')
+  if (this.query !== null && typeof this.query === 'object') {
+    if (querystring === undefined) querystring = require('querystring');
     query = querystring.stringify(this.query);
+  }
 
   var search = this.search || (query && ('?' + query)) || '';