exp-fetch

fetch

A small and pluggable lib to fetch a resource and cache the result.

Caching

Fetch will parse the cache-control header. I it encounters private, no-cache, max-age=0 or must-revalidate it wont cache. Otherwise it will respect the max-age header.

Callback usage:

var behavior = {};
var fetch = fetchBuilder(behavior);
fetch("http://example.com/resouce.json", function (err, content) {
    // Do something with the result
});

Promise usage:

var behavior = {};
var fetch = fetchBuilder(behavior);
fetch("http://example.com/resouce.json").then(function (content) {
    // Do something with the result
});

Allowed behavior options

• freeze: (default:false). When this option is set it will freeze the response so it can't be modified.
• cache: (default: an instance of AsyncCache (https://github.com/ExpressenAB/exp-asynccache). To disable caching set {cache: null}
• cacheKeyFn: (default: caches on the url) An optional formatting function for finding the cache-key. One might, for example, want to cache on an url with the get params stripped.
• maxAgeFn: (default: respects the cache-control header)
• onNotFound: If given a function, it will be called each time fetch encounters a 404
• onError: If given a function, it will be called each time fetch encounters a non 200 nor 404 response
• onSuccess: If given a function, it will be called each time fetch encounters a 200
• logger: A logger object implementing error, warning, info, debug for example https://github.com/tj/log.js

CacheKeyFn

var keyFinder = function (url) {
    return url.replace(/\//g, "");
}
var fetch = fetchBuilder({cacheKeyFn: keyFinder});
Promise.all([
   fetch("http://example.com/foo/bar")
   fetch("http://example.com/foobar")
]).then(function (result) {
   result[0] === result[1];
});

maxAgeFn

function cacheNothing(maxAge, key, headers, content) {
    return -1;
}
var fetch = fetchBuilder({maxAgeFn: cacheNothing});