map layer management

api/http.ts

@@ -0,0 +1,22 @@
+export class ApiError extends Error {
+    status: number;
+    body: string;
+
+    constructor(message: string, status: number, body: string) {
+        super(message);
+        this.name = "ApiError";
+        this.status = status;
+        this.body = body;
+    }
+}
+
+export async function requestJson<T>(input: RequestInfo | URL, init?: RequestInit): Promise<T> {
+    const res = await fetch(input, init);
+
+    if (!res.ok) {
+        const text = await res.text();
+        throw new ApiError(`Request failed with status ${res.status}`, res.status, text);
+    }
+
+    return (await res.json()) as T;
+}