update readme

README.md

@@ -123,10 +123,11 @@ Options:
 ```js
 {
   ttl: 1000, // Time to live. How long (in ms) responses remain cached before being automatically ejected. If undefined, responses are never automatically ejected from the cache.
-  global: true, // If true, uses the global cache, which is shared together by all MemoryCaches that specify this option. If false (or undefined), every MemoryCache uses a separate cache.
 }
 ```
 
+Note that by default (if you don't use `withCache()`) a **shared** MemoryCache will be used (you can import this module in multiple files and they will all share the same cache). If you instantiate and provide a `new MemoryCache()` as shown above however, the cache is *NOT* shared unless you explicitly pass it around and pass it into `withCache()` in each of your source files.
+
 ### FileSystemCache
 
 Cache to a directory on disk. This allows the cache to survive the process exiting.
@@ -147,14 +148,18 @@ const fetch = fetchBuilder.withCache(new FileSystemCache(options));
 
 ### Provide Your Own
 
-You can implement a caching layer yourself. The cache simply needs to be an object that has `get(key)` and `set(key, value)` functions.
+You can implement a caching delegate yourself. The cache simply needs to be an object that has `set(key, value)`, `get(key)`, and `remove(key)` functions.
 
 The set function must accept a key (which will be a string) and a value (which will be a JSON-serializable JS object) and store them.
 
 The get function should accept a key and return whatever value was set for that key (or `undefined`/`null` if there is no value for that key).
 
+The remove function should accept a key and remove the cached value associated with that key, if any.
+
 Both functions can be async.
 
+It is safe to remove values from the cache arbitrarily (for example if you implement a TTL in the caching delegate).
+
 For example you could make and use your own simple memory cache like this:
 
 ```js

classes/caching/file_system_cache.js

@@ -26,4 +26,4 @@ module.exports = class FileSystemCache {
       this.keyTimeout.updateTimeout(key, this.ttl, () => this.remove(key));
     }
   }
-}
+};

classes/caching/key_timeout.js

@@ -13,4 +13,4 @@ module.exports = class KeyTimeout {
       callback();
     }, durationMs);
   }
-}
+};

classes/caching/memory_cache.js

@@ -4,14 +4,7 @@ module.exports = class MemoryCache {
   constructor(options = {}) {
     this.ttl = options.ttl;
     this.keyTimeout = new KeyTimeout();
-
-    if (options.global && !globalThis.nodeFetchCache) {
-      globalThis.nodeFetchCache = {};
-    }
-
-    this.cache = options.global
-      ? globalThis.nodeFetchCache
-      : {};
+    this.cache = {};
   }
 
   get(key) {
@@ -30,4 +23,4 @@ module.exports = class MemoryCache {
       this.keyTimeout.updateTimeout(key, this.ttl, () => this.remove(key));
     }
   }
-}
+};

classes/response.js

@@ -1,4 +1,3 @@
-const fs = require('fs');
 const stream = require('stream');
 const Headers = require('./headers.js');
 

index.js

@@ -2,7 +2,6 @@ const fetch = require('node-fetch');
 const fs = require('fs');
 const { URLSearchParams } = require('url');
 const crypto = require('crypto');
-const path = require('path');
 const Response = require('./classes/response.js');
 const MemoryCache = require('./classes/caching/memory_cache.js');
 
@@ -97,19 +96,18 @@ async function getResponse(cache, requestArguments) {
 
   if (cachedValue) {
     return new Response(cachedValue, ejectSelfFromCache, true);
-  } else {
-    const fetchResponse = await fetch(...requestArguments);
-    const rawResponse = await createRawResponse(fetchResponse);
-    await cache.set(cacheKey, rawResponse);
-    return new Response(rawResponse, ejectSelfFromCache, false);
   }
+  const fetchResponse = await fetch(...requestArguments);
+  const rawResponse = await createRawResponse(fetchResponse);
+  await cache.set(cacheKey, rawResponse);
+  return new Response(rawResponse, ejectSelfFromCache, false);
 }
 
 function createFetchWithCache(cache) {
-  const fetch = (...args) => getResponse(cache, args);
-  fetch.withCache = createFetchWithCache;
+  const fetchCache = (...args) => getResponse(cache, args);
+  fetchCache.withCache = createFetchWithCache;
 
-  return fetch;
+  return fetchCache;
 }
 
 module.exports = createFetchWithCache(new MemoryCache());