function-from-file

Node.js module for extracting function from given javascript file (great for unit testing).

• both sync or async options
• reach private functions also
• simple way of mocking inner dependecies

One condition only: "function must have a name".

Keywords: functions, private function, unit tests, unittest, testing, get function, extract function, parse function, find function.

Example

var getFunction = require("function-from-file");
var privateFunction = getFunction('./foo/bar.js', 'someFunction');

// you can use imported function now
privateFunction();

Motivation

When writing unit tests, private functions inside your module are not accessible from outside (via require statement). With this tool you can get and test any function by its name.

Installation

Use --save-dev parameter if you are going use this module just for development (e.g. testing) or --save if your application is using it.

$ npm install function-from-file --save-dev

Features / API

Sync

This example extracts a function addNumbers from script ./foo/bar.js

var add = getFunction('./foo/bar.js', 'addNumbers');
var result = add(100, 50);

Get more functions at once

If array of function names is given, returns an object where keys are those functions.

var fns = getFunction('./foo/bar.js', ['foo', 'bar']);
fns.foo();
fns.bar();

Async

To get a function asynchronous add the last parameter as a callback function:

getFunction('./foo/bar.js', 'addNumbers', function(err, result) {
    if (err) throw err;
    console.log( result(100, 50) );
});

It works with more function names also (like the sync variant):

getFunction('./foo/bar.js', ['foo', 'bar'], function(err, result) {
    if (err) throw err;
    result.foo();
    result.bar();
});

Mock dependecies

Sometimes you extract function that has some dependencies on other functions or variables. See this example:

// File foo/bar.js

var koef = 8;
function multiplier(a) {
    return a * koef;
}

When you extract function (not working solution):

var fn = getFunction('./foo/bar.js', 'multiplier');
fn(2);

This code throws error: Uncaught ReferenceError: koef is not defined.

Working solution is to mock (define localy) all the dependencies:

var fn = getFunction('./foo/bar.js', 'multiplier');
var koef = 8;
eval('var mockedFn = '+fn);
mockedFn(4);

The function fn in eval statement was converted to string so it evals:

eval("var mockedFn = function multiplier(a) { return a * koef; }");

Now it uses the local variable koef.

Caching

The most expensive operation is reading a file and parsing a source code and looking for a functions. So this is why caching is implemented. When you are getting function from the same file, cached result is used. Caching is default turned on, but you can turn it off.

Disable cache

To turn the caching off call the:

var getFunction = require("function-from-file");
getFunction.disableCache();

Enable cache

To turn the caching on call the:

var getFunction = require("function-from-file");
getFunction.enableCache();

Clear cache

To clear the cache call the:

var getFunction = require("function-from-file");
getFunction.clearCache();

Tests

To run the tests, at first install the dependencies: $ npm install

Running unit tests: $ npm test

Running coverage tests: $ npm run test-cov

Author

Johnny Seyd at GitHub <[email protected]>

Credits

Build on the module function-extractor, based on esprima and other included submodules.

License

BSD