docs: improve code comments

Author: anonrig

README.md

@@ -48,17 +48,17 @@ console.log(qs.stringify({ foo: ['bar', 'baz'] }))
 ╔═════════════════════════════════════════╤═════════╤═══════════════════╤═══════════╗
 ║ Slower tests                            │ Samples │            Result │ Tolerance ║
 ╟─────────────────────────────────────────┼─────────┼───────────────────┼───────────╢
-║ qs                                      │   10000 │  314822.82 op/sec │  ± 1.12 % ║
-║ query-string                            │    1000 │  330364.46 op/sec │  ± 0.89 % ║
-║ querystringify                          │   10000 │  442352.24 op/sec │  ± 1.31 % ║
-║ @aws-sdk/querystring-parser             │   10000 │  471561.65 op/sec │  ± 1.12 % ║
-║ URLSearchParams-with-Object.fromEntries │   10000 │  865453.19 op/sec │  ± 2.29 % ║
-║ URLSearchParams-with-construct          │   10000 │ 1234031.63 op/sec │  ± 3.12 % ║
-║ node:querystring                        │   10000 │ 1484397.94 op/sec │  ± 2.46 % ║
+║ qs                                      │   10000 │  317841.53 op/sec │  ± 1.18 % ║
+║ query-string                            │   10000 │  341009.91 op/sec │  ± 1.06 % ║
+║ querystringify                          │    1000 │  451609.79 op/sec │  ± 0.61 % ║
+║ @aws-sdk/querystring-parser             │    1000 │  477241.09 op/sec │  ± 0.69 % ║
+║ URLSearchParams-with-Object.fromEntries │   10000 │  870095.07 op/sec │  ± 3.29 % ║
+║ URLSearchParams-with-construct          │   10000 │ 1232650.60 op/sec │  ± 2.95 % ║
+║ node:querystring                        │   10000 │ 1462802.04 op/sec │  ± 3.69 % ║
 ╟─────────────────────────────────────────┼─────────┼───────────────────┼───────────╢
 ║ Fastest test                            │ Samples │            Result │ Tolerance ║
 ╟─────────────────────────────────────────┼─────────┼───────────────────┼───────────╢
-║ fast-querystring                        │   10000 │ 1798615.82 op/sec │  ± 2.65 % ║
+║ fast-querystring                        │   10000 │ 1809816.84 op/sec │  ± 3.19 % ║
 ╚═════════════════════════════════════════╧═════════╧═══════════════════╧═══════════╝
 ```
 

lib/parse.js

@@ -35,10 +35,9 @@ function parse(input) {
     if (c === 38 || c === -1) {
       hasBothKeyValuePair = equalityIndex > startingIndex;
       keyEndingIndex = hasBothKeyValuePair ? equalityIndex : i;
-
       key = input.slice(startingIndex + 1, keyEndingIndex);
 
-      // Check if the current range consist of a single key
+      // Only update value if '=' exists in the current range
       if (hasBothKeyValuePair) {
         value = input.slice(equalityIndex + 1, i);
       }
@@ -70,6 +69,7 @@ function parse(input) {
         } else {
           const currentValue = result[key];
 
+          // Optimization: value.pop is faster than Array.isArray(value)
           if (currentValue.pop) {
             currentValue.push(value);
           } else {
@@ -79,7 +79,6 @@ function parse(input) {
       }
 
       // Reset reading key value pairs
-      key = "";
       value = "";
       startingIndex = i;
       equalityIndex = i;
@@ -98,7 +97,7 @@ function parse(input) {
         equalityIndex = i;
       }
     }
-    // Check '+', and replace it with empty space.
+    // Check '+', and remember to replace it with empty space.
     else if (c === 43) {
       if (equalityIndex <= startingIndex) {
         keyHasPlus = true;