Fix: Cannot read property 'then' of undefined (#188)

* prefetch returns promise instead of undefined

* prefetch returns promise instead of undefined

Co-authored-by: Lee Powell <[email protected]>

Author: leepowelldev

src/chunks.mjs

@@ -121,7 +121,12 @@ export function listen(options) {
 export function prefetch(url, isPriority, conn) {
   if (conn = navigator.connection) {
     // Don't prefetch if using 2G or if Save-Data is enabled.
-    if (conn.saveData || /2g/.test(conn.effectiveType)) return;
+    if (conn.saveData) {
+      return Promise.reject(new Error('Cannot prefetch, Save-Data is enabled'));
+    }
+    if (/2g/.test(conn.effectiveType)) {
+      return Promise.reject(new Error('Cannot prefetch, network conditions are poor'));
+    }
   }
 
   // Dev must supply own catch()
@@ -138,4 +143,4 @@ export function prefetch(url, isPriority, conn) {
       }
     })
   );
-}
+}

src/index.mjs

@@ -114,7 +114,12 @@ export function listen(options) {
 export function prefetch(url, isPriority, conn) {
   if (conn = navigator.connection) {
     // Don't prefetch if using 2G or if Save-Data is enabled.
-    if (conn.saveData || /2g/.test(conn.effectiveType)) return;
+    if (conn.saveData) {
+      return Promise.reject(new Error('Cannot prefetch, Save-Data is enabled'));
+    }
+    if (/2g/.test(conn.effectiveType)) {
+      return Promise.reject(new Error('Cannot prefetch, network conditions are poor'));
+    }
   }
 
   // Dev must supply own catch()