Execute script.onload/onerror

Add object-support for URLSearchParams. Start to treat js.Value as a first
class object (instead of js.Object, where appropriate).

src/browser/webapi/net/Fetch.zig

@@ -34,6 +34,7 @@ const IS_DEBUG = @import("builtin").mode == .Debug;
 const Fetch = @This();
 
 _page: *Page,
+_url: []const u8,
 _buf: std.ArrayList(u8),
 _response: *Response,
 _resolver: js.PersistentPromiseResolver,
@@ -48,6 +49,7 @@ pub fn init(input: Input, page: *Page) !js.Promise {
     fetch.* = .{
         ._page = page,
         ._buf = .empty,
+        ._url = try page.arena.dupe(u8, request._url),
         ._resolver = try page.js.createPromiseResolver(.page),
         ._response = try Response.init(null, .{ .status = 0 }, page),
     };
@@ -58,6 +60,7 @@ pub fn init(input: Input, page: *Page) !js.Promise {
     if (comptime IS_DEBUG) {
         log.debug(.http, "fetch", .{ .url = request._url });
     }
+    std.debug.print("fetch: {s}\n", .{request._url});
 
     try http_client.request(.{
         .ctx = fetch,
@@ -97,6 +100,7 @@ fn httpDataCallback(transfer: *Http.Transfer, data: []const u8) !void {
 fn httpDoneCallback(ctx: *anyopaque) !void {
     const self: *Fetch = @ptrCast(@alignCast(ctx));
     self._response._body = self._buf.items;
+    std.debug.print("fetch-resolve: {s}\n", .{self._url});
     return self._resolver.resolve(self._response);
 }