perf: improve stringify performance

Author: anonrig

lib/stringify.js

@@ -28,13 +28,17 @@ function getAsPrimitive(value) {
 function stringify(input) {
   let result = "";
 
+  if (input === null || typeof input !== 'object') {
+    return result;
+  }
+
   const keys = Object.keys(input);
   const keyLength = keys.length;
 
   for (let i = 0; i < keyLength; i++) {
     const key = keys[i];
     const value = input[key];
-    const encodedKey = encodeString(key);
+    const encodedKey = encodeString(key) + "=";
 
     if (i) {
       result += "&";
@@ -47,10 +51,10 @@ function stringify(input) {
           result += "&";
         }
 
-        result += encodedKey + "=" + getAsPrimitive(value[j]);
+        result += encodedKey + getAsPrimitive(value[j]);
       }
     } else {
-      result += encodedKey + "=" + getAsPrimitive(value);
+      result += encodedKey + getAsPrimitive(value);
     }
   }