🐛 Query addon should strip undefined values

Should solve #148

src/addons/queryString.ts

@@ -1,5 +1,9 @@
 import type { Wretch, Config, WretchAddon } from "../types.js"
 
+function stringify(value?: string | null): string | null {
+  return typeof value !== "undefined" ? value : ""
+}
+
 const appendQueryParams = (url: string, qp: object | string, replace: boolean, config: Config) => {
   let queryString: string
 
@@ -8,11 +12,12 @@ const appendQueryParams = (url: string, qp: object | string, replace: boolean, c
   } else {
     const usp = config.polyfill("URLSearchParams", true, true)
     for (const key in qp) {
+      const value = qp[key]
       if (qp[key] instanceof Array) {
-        for (const val of qp[key])
-          usp.append(key, val)
+        for (const val of value)
+          usp.append(key, stringify(val))
       } else {
-        usp.append(key, qp[key])
+        usp.append(key, stringify(value))
       }
     }
     queryString = usp.toString()

test/node/wretch.spec.ts

@@ -663,6 +663,12 @@ describe("Wretch", function () {
     expect(w.query({}, true)._url).toBe(_URL)
     expect(w.query({ a: 1 }).query({}, true)._url).toBe(_URL)
   })
+
+  it("should strip undefined values", function () {
+    const w = wretch(_URL).addon(QueryStringAddon)
+    expect(w.query({ a: undefined, b: 1 })._url).toBe(_URL + "?a=&b=1")
+    expect(w.query({ array: ["a", "b", undefined, "c"] })._url).toBe(_URL + "?array=a&array=b&array=&array=c")
+  })
 })
 
 describe("Mix", function () {