url: improve URLSearchParams.toString() performance

Refs: nodejs/performance#56

Author: debadree25

benchmark/url/url-searchparams-toString.js

@@ -0,0 +1,21 @@
+'use strict';
+const common = require('../common.js');
+
+const bench = common.createBenchmark(main, {
+  n: [1e6],
+});
+
+const value = {
+  str: 'foo',
+  array: ['bar', 'baz', 'bal'],
+  bool: true,
+  bigInt: BigInt(100),
+  num: 256,
+};
+
+function main({ n }) {
+  bench.start();
+  for (let i = 0; i < n; i++)
+    new URLSearchParams(value).toString();
+  bench.end(n);
+}

lib/internal/url.js

@@ -2,6 +2,7 @@
 
 const {
   Array,
+  ArrayIsArray,
   ArrayPrototypeJoin,
   ArrayPrototypeMap,
   ArrayPrototypePush,
@@ -211,7 +212,17 @@ class URLSearchParams {
           const desc = ReflectGetOwnPropertyDescriptor(init, key);
           if (desc !== undefined && desc.enumerable) {
             const typedKey = toUSVString(key);
-            const typedValue = toUSVString(init[key]);
+            let typedValue = '';
+            if (ArrayIsArray(init[key])) {
+              const len = init[key].length;
+              for (let j = 0; j < len; j++) {
+                typedValue += toUSVString(init[key][j]);
+                if (j < len - 1)
+                  typedValue += ',';
+              }
+            } else {
+              typedValue = toUSVString(init[key]);
+            }
 
             // Two different key may result same after `toUSVString()`, we only
             // leave the later one. Refers to WPT.
@@ -1017,12 +1028,17 @@ function serializeParams(array) {
 
   const firstEncodedParam = encodeStr(array[0], noEscape, paramHexTable);
   const firstEncodedValue = encodeStr(array[1], noEscape, paramHexTable);
-  let output = `${firstEncodedParam}=${firstEncodedValue}`;
+  let output = firstEncodedParam;
+  output += '=';
+  output += firstEncodedValue;
 
   for (let i = 2; i < len; i += 2) {
     const encodedParam = encodeStr(array[i], noEscape, paramHexTable);
     const encodedValue = encodeStr(array[i + 1], noEscape, paramHexTable);
-    output += `&${encodedParam}=${encodedValue}`;
+    output += '&';
+    output += encodedParam;
+    output += '=';
+    output += encodedValue;
   }
 
   return output;