utils.ts•1.36 kB
export function withCors<Props>({
getCorsHeaders,
handler,
}: {
getCorsHeaders(
request: Request,
): Record<string, string> | Headers | null | undefined
handler: EpicMeExportedHandler<Props>['fetch']
}): EpicMeExportedHandler<Props>['fetch'] {
return async (request, env, ctx) => {
const corsHeaders = getCorsHeaders(request)
if (!corsHeaders) {
return handler(request, env, ctx)
}
// Handle CORS preflight requests
if (request.method === 'OPTIONS') {
const headers = mergeHeaders(corsHeaders, {
'Access-Control-Max-Age': '86400',
})
return new Response(null, { status: 204, headers })
}
// Call the original handler
const response = await handler(request, env, ctx)
// Add CORS headers to ALL responses, including early returns
const newHeaders = mergeHeaders(response.headers, corsHeaders)
return new Response(response.body, {
status: response.status,
statusText: response.statusText,
headers: newHeaders,
})
}
}
/**
* Merge multiple headers objects into one (uses set so headers are overridden)
*/
export function mergeHeaders(
...headers: Array<ResponseInit['headers'] | null | undefined>
) {
const merged = new Headers()
for (const header of headers) {
if (!header) continue
for (const [key, value] of new Headers(header).entries()) {
merged.set(key, value)
}
}
return merged
}