Implement preventCallFetch option

Author: ilyalesik

README.md

@@ -51,11 +51,21 @@ const { isLoading, data } = useFetch("https://swapi.co/api/people/1", {
 });
 
 ```
-
+### Custom formatter
 You can pass *formatter* prop for using custom formatter function. Default is used *response => response.json()* formatter.
 ```javascript
 const { isLoading, data } = useFetch("https://swapi.co/api/people/1", {
     formatter: (response) => response.text()
 });
 
 ```
+### Prevent call `fetch`
+For prevent call fetch you can pass *preventCallFetch* prop:
+
+```javascript
+const {authToken} = useContext(authTokenContext);
+const { isLoading, data } = useFetch("https://swapi.co/api/people/1", {
+    preventCallFetch: !authToken //don't call request, if haven't authToken
+});
+
+```

package.json

@@ -1,6 +1,6 @@
 {
   "name": "react-fetch-hook",
-  "version": "1.2.4",
+  "version": "1.3.0",
   "description": "React fetch hook",
   "main": "./dist/index.js",
   "scripts": {

src/__tests__/useFetch.test.js

@@ -80,6 +80,29 @@ describe("useFetch", () => {
         });
     });
 
+    it("call with url, options with preventCallFetch", async () => {
+        fetch.mockResponse(JSON.stringify({ data: "12345" }));
+        const options = {
+            headers: {
+                Accept: "application/json, application/xml, text/plain, text/html, *.*",
+                "Content-Type": "application/json; charset=utf-8"
+            }
+        };
+
+        const Component = () => {
+            const result = useFetch("https://google.com", { ...options, preventCallFetch: true });
+            return <div>{result.data}</div>;
+        };
+
+        const { container, rerender } = render(<Component />);
+
+        await wait(() => {
+            rerender(<Component />);
+
+            expect(fetch.mock.calls.length).toEqual(0);
+        });
+    });
+
     it("error on throw error", async () => {
         fetch.mockReject(new Error("fake error message"));
 

src/useFetch.js

@@ -9,7 +9,7 @@ type TUseFetchResult<T> = {
 
 export function useFetch<T>(
     path: RequestInfo,
-    options?: { ...RequestOptions, formatter?: Response => Promise<T> }
+    options?: { ...RequestOptions, formatter?: Response => Promise<T>, preventCallFetch?: boolean }
 ): TUseFetchResult<T> {
     const defaultFormatter = response => {
         if (!response.ok) {
@@ -18,7 +18,11 @@ export function useFetch<T>(
         return response.json();
     };
     const fetchInstance = formatter => (path, options) => {
-        return fetch(path, options).then((typeof formatter === "function" && formatter) || defaultFormatter);
+        const { preventCallFetch, ...otherOptions } = options || {};
+        if (preventCallFetch) {
+            return Promise.resolve();
+        }
+        return fetch(path, otherOptions).then((typeof formatter === "function" && formatter) || defaultFormatter);
     };
     if (options) {
         const { formatter, ...fetchOptions } = options;