CODEWITHSUNDEEP
javascriptdesign-patternsnode.jsrequirejs
lostinplace
lostinplace

Reputation: 1518

How does the require object as defined inside of node.js global work?

ok, I'm kind of stumped.

If you open up a node window and type this.require you get:

[Function: require]
resolve: [Function],
main: undefined,
extensions:
{ '.js': [Function],
  '.json': [Function],
  '.node': [Function] },
registerExtension: [Function],
cache: {} }

This means that the function require(args) was created as let's say, require=function(){return resultOfOperation}

THEN someone went ahead and said, require.cache={} I'm fine with all that, but is the cache object of any use to the require(args) function? the requirejs sources makes no mention of a cache object at all, so I'm wondering if I'm running into a different module loader or if this is just something that nodejs uses to track some other behavior.

Question is, "Can/(How can) a function that has been assigned additional properties access those properties from within the executing body of code?" (preferably without knowledge of a superior function)

Note, I understand that this is possibly just written into the engine in c++, I'm just interested to see whether people can think of a way to do this in javascript

Upvotes: 3

Views: 1331

Answers (2)

Linus Thiel
Linus Thiel

Reputation: 39261

First off, there seems to be some confusion. Node's require is not RequireJS. They are two completely different things.

To learn more about node's module system, here are the relevant docs. Here are docs on require.

To answer your second question, functions in javascript are objects. One way to accomplish something like what you describe above:

var foo = function() {
    console.log(foo.cache);
};

foo.cache = {
    bar: 1
};

foo();
// Outputs { bar: 1 }

Another way uses the deprecated arguments.callee (so don't do this at home):

var foo = function() {
    console.log(arguments.callee.cache);
};

foo.cache = {
    bar: 1
};

foo();
// Outputs { bar: 1 }

Upvotes: 4

seppo0010
seppo0010

Reputation: 15889

Your last question:

Can/(How can) a function that has been assigned additional properties access those properties from within the executing body of code?

You can use the global name of the function. For example

var myFunc = function() {
    console.log(myFunc.a++);
}
myFunc.a = 1;
myFunc();
myFunc();

Will output

1
2

Now, your other question

I'm fine with all that, but is the cache object of any use to the require(args) function?

Yes, require.cache is used so when you load twice the same module, it returns the same object and doesn't really load the script again. Check out node.js documentation on require.cache: http://nodejs.org/api/globals.html#globals_require_cache

Upvotes: 4

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