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Node's require, but lazy loading
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README.md

lazy_require

npm tests

Like require, but the library is only actually loaded when it's used.

Note: This project is in early development, and versioning is a little different. Read this for more details.

Why should you care?

With node's standard require function, as soon as it is run, it loads the linked module along with anything else it requires etc. down the tree. For larger dependencies, this can take a while -- I've seen larger libraries soak up 500ms+ of load time off a require call.

At the same time, in 99% of cases, you do not actually need a required module to be executed immediately, you only need it to be executed when it's used. But since the convention in node is to load all dependencies at the top of each file, you are always taking on the entire dependency load upfront no matter when, whether you actually end up making a call to that module that uses all of its dependencies. For example, let's look at a basic example module, which serves as an API for interacting with doges:

var DogeCreator = require('foo'),
    DogePetter = require('bar');

module.exports = {
  createDoge: function(name){ return new DogeCreator(name) },
  petDoge: function(){ DogePetter.pet(); return true }
}

Now, let's look at another file that requires and uses this module:

var dogeAPI = require('dogeAPI');

dogeAPI.createDoge('fluffy');

In this example, although we only used the DogeCreator library, we fully loaded both DogeCreator and DogePetter. So if DogePetter was a heavy library, you are simply wasting the time it takes to load that dependency.

What lazy_require does is solves this exact issue. You can lazy_require a module, but the module will only actually be loaded once you use it. So if we used lazy_require in the example above rather than require, we would not load DogePetter at all, saving any time it took to load that entire module (and its dependency tree).

Installation

npm install lazy_require

Usage

Lazy require is a hacky hack, but it works, and is, as far as I know, entirely safe. But because it's a hack, it's not quite as smooth as the built in require in some ways. By default, it will assign the library name you pass it to a variable of the same name. For example:

lazy_require('fs');
console.log(fs); // it's defined!

However, if you want to assign it to a specific name, you need to pass that as the second parameter. For example:

lazy_require('../lib/doge_api', 'doge')
console.log(doge); // it works!

Do not try to use the output of lazy_require like you would with a normal require -- the assignment has to happen through the second parameter. That's all!

License & Contributing

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