Web Development – Add JavaScript to All Pages or Only Required Pages for Better Performance?

Unless I'm misunderstanding the question, I don't think that this is an appropriate scenario for caching.

Cached data normally has at least one of the following attributes (usually all of them):

• Expensive to retrieve or compute;
• Highly static - may change occasionally but very rarely;
• Non-critical - OK if the requester sees stale data.

It doesn't sound like any of these apply to your situation.

• The query is a simple SELECT, probably TOP N, just an index seek;
• It changes very frequently;
• Your requirements indicate that immediate updates are required.

So why are you caching? Caching isn't a panacea; oftentimes it can actually make performance worse, if the cache memory could be better used for some other purpose.

Databases do their own caching. As long as the DB server has plenty of memory then it may cache the entire table in memory if it's frequently queried; the performance of that will be just as good as your cache if not better.

Some further thoughts/suggestions:

• If stale data is OK, then the simplest solution would be to use a fixed interval (i.e. expiration). This method is used very effectively in hundreds of thousands of sites and systems. You can either force an update on expiration or just wait until it's requested again.

• If you're concerned about conflicts between reads and writes, then (a) don't be, until you've profiled it, and (b) if it really is an issue then instead of trying to cache it, just use a redundant table or a NOLOCK hint.

If you need to invalidate the cache every single time a row is added/changed then you have completely defeated the purpose of an application cache, and are now trying to implement an in-memory database. Please don't do this unless you have an extremely good reason for it.

The JavaScript standards committee updates JavaScript annually. Browser Support Varies. Tooling is available to help.

Javascript is defined by the ECMA-262 standard, which is updated anually. Every revision has added some new syntax. All browsers since IE5 support a common subset of syntax in the same way, it's only a question of if they support new syntax options or not. However, since syntax extensions can be as small as Allowing trailing commas in parameter lists, it's not always obvious which options you are using. Here's a list of the changes since they went to annual updates.

It is common practice (in 2021,) to include a build step for your JavaScript that replaces newer syntax with older syntax so that code can be run in older browsers that are not updated. Babel, Browserslist, and @babel/preset-env make it easy to support a configurable set of browsers. (As long as you're still developing your site!)