How to cache .js file at client side in node js

You can serve static files (html, css or js) with express by using express.static, pointing to a folder in your project, like this:

app.use(express.static(__dirname + '/public'));

See this link for more information: http://blog.modulus.io/nodejs-and-express-static-content

The browser should do this caching work for you, but it seems you need to implement this by yourself. If you still need to implement your own cache, take this into account:

• You will need a method to save the cache entries
• You will need a caching policy (e.g. when to uncaching, etc...)

For the first issue, I suggest to use browser side persistence, I do not recommend using localStorage, cookie or similar since it is not 100% cross-browser, instead , I do recommend using shims like persist.js https://github.com/jeremydurham/persist-js

To address the second problem, I suggest using IDs for the files, these IDs can be computed on server side from content (using SHA digest), this would allow you to change the JS file when needed (identity based on content, like GIT)

For example, you can do this

store = new Persist.Store('My Application');
function loadCachedJs(sha, loadedCallback) {
  var jsCode = store.get(sha);
  if (jsCode) {
    // the js is on cache!, you can load it without going to server
    setTimeout(
      function() {
        eval(jsCode);
        loadedCallback();
      }
    );
  } else {
    // the js is not on cache, you need to go to server
    // but is only for this first time
    $.get("/.../.../" + sha + ".js", function(res) {
      // store the result on cache
      storeJsOnCache(sha, res.data);
      eval(res.data);
      loadedCallback();
    });
  }
}
function storeJsOnCache(jsCode) {
  store.set(sha, jsCode);
}

Then, on certain section of your code, you get "load the js file of certain sha", you call loadCachedJs:

...
loadCachedJs(sha, function() {
  // JS loaded, do what you need to do with this js file
});

And, on server side, you will need to implement the endpoint returning the JS corresponding to SHA