feat: add repeatArrayParams option

packages/better-fetch/src/test/fetch.test.ts

@@ -566,19 +566,33 @@ describe("url", () => {
 		expect(url.toString()).toBe("http://localhost:4001/param/%23test/item%201");
 	});
 
-	it("should expand array values into multiple query parameters", () => {
+	it("should expand array values into multiple query parameters when repeatArrayParams is true", () => {
 		const url = getURL("/test", {
 			query: {
 				filterValue: ["admin", "user"],
 			},
 			baseURL: "http://localhost:4000",
+			repeatArrayParams: true,
 		});
 
 		expect(url.toString()).toBe(
 			"http://localhost:4000/test?filterValue=admin&filterValue=user",
 		);
 	});
 
+	it("should preserve arrays as JSON strings", () => {
+		const url = getURL("/test", {
+			query: {
+				filterValue: ["admin", "user"],
+			},
+			baseURL: "http://localhost:4000",
+		});
+
+		expect(url.toString()).toBe(
+			"http://localhost:4000/test?filterValue=%5B%22admin%22%2C%22user%22%5D",
+		);
+	});
+
 	it("should preserve objects as JSON strings", () => {
 		const url = getURL("/test", {
 			query: {

packages/better-fetch/src/types.ts

@@ -77,6 +77,13 @@ export type BetterFetchOption<
 			 * Query parameters (key-value pairs)
 			 */
 			query?: Query;
+			/**
+			 * When true, array query parameters are encoded as repeated keys 
+			 * (e.g. `?foo=a&foo=b&foo=c`) instead of JSON (`?foo=["a","b","c"]`).
+			 * 
+			 * @default false - Arrays are encoded as JSON by default.
+			 */
+			repeatArrayParams?: boolean;
 			/**
 			 * Dynamic parameters.
 			 *

packages/better-fetch/src/url.ts

@@ -32,7 +32,7 @@ export function getURL(url: string, option?: BetterFetchOption) {
 		let serializedValue;
 		if (typeof value === "string") {
 			serializedValue = value;
-		} else if (Array.isArray(value)) {
+		} else if (option?.repeatArrayParams && Array.isArray(value)) {
 			for (const val of value) {
 				queryParams.append(key, val);
 			}