@ndcode/min_js_cache

Build Cache wrapper for minifying JavaScript files

An NDCODE project.

Overview

The min_js_cache package exports a single constructor MinJSCache(diag) which must be called with the new operator. The resulting cache object stores the utf-8-encoded text of JavaScript files loaded from disk and minified.

See the build_cache, disk_build, and uglify-es packages for more information. The MinJSCache object is essentially a wrapper object which routes the request between these packages, to ensure that the minified JavaScript text is either retrieved from RAM or minified from a source file as required.

Calling API

Suppose one has a MinJSCache instance named mjc. It behaves somewhat like an ES6 Map object, except that it only has the mjc.get() function, because new objects are added to the cache by attempting to get them.

The interface for the MinJSCache-provided instance function mjc.get() is:

await mjc.get(key) — retrieves the object stored under key, where key is the on-disk pathname to a JavaScript file. A Buffer object is returned, containing the utf-8-encoded text resulting from running uglify-es on the source file. The pathname and the returned result are cached for future reuse.

Before returning the cached copy, the existence and modification time of the JavaScript file on disk is checked to make sure that the cache is up-to-date. Otherwise, if the file doesn't exist an ENOENT exception is thrown, or if the file exists it is loaded and minified and the cache updated for next time. The minification is via disk, and skipped if an up-to-date disk result is present.

About diagnostics

The diag argument to the constructor is a bool, which if true causes messages to be printed via console.log() for all activities except for the common case of retrieval when the object is already up-to-date. A diag value of undefined is treated as false, thus it can be omitted in the usual case.

To be implemented

The uglify-es package is called with standard NDCODE options. This is part of the reason to have min_js_cache, so as to provide a consistent interface to minifiers for JavaScript, CSS, SVG and so on. However, if some control of the underlying minifier is needed in future, we could add an options object to pass through, in which we'd inject our NDCODE options where not overridden.

It is intended that we will shortly add a timer function (or possibly just a function that the user should call periodically) to flush built templates from the cache after a stale time. There is otherwise no way to delete an object from the cache, except by first deleting it on disk, then trying to get it.

GIT repository

The development version can be cloned, downloaded, or browsed with gitweb at: https://git.ndcode.org/public/min_js_cache.git

License

All of our NPM packages are MIT licensed, please see LICENSE in the repository.

Contributions

The caching system is under active development (and is part of a larger project that is also under development) and thus the API is tentative. Please go ahead and incorporate the system into your project, or try out our example webserver built on the system, subject to the caution that the API could change. Please send us your experience and feedback, and let us know of improvements you make.

Contact: Nick Downing [e-mail]