cmem

Small and basic function stubbing module. Primarily used in unit testing.

var assert = require('assert');
var cmem = require('cmem');
var stub = cmem();
var object = { fn: stub };

object.fn(1);
stub(2);
object.fn(3);

assert.deepEqual(stub.$select('$this === $[0]', '$args[0]', object), [ 1, 3 ]);

Installation

$ npm install cmem

Features

Function call registry
Mapping and filtering arguments and contexts of function calls
Function wrapping and switching
Creating function with fixed result

API

cmem( [ fn ] )

Creates new cmem instance. Optional fn argument can be passed as wrapped function.

setTimeout = cmem(setTimeout);
setTimeout(function () { console.log('after some time'); }, 100);
assert.equal(setTimeout.$count, 1);
assert.equal(setTimeout.$args[1], 100);

cmem.create()

Creates new cmem factory.

cmem.clear()

Clears all cmem instances.

cmem.unit( value )

Helper method: creates function that always returns passed argument.

assert.equal(cmem.unit('some value')(), 'some value');

cmem.iterator( pattern, [ arg ], ... );

Helper method: creates iterator function from string. Usefull for map, filter, etc... array methods.

var iter = cmem.iterator('$item + $[0]', 1);
assert.deepEqual([ 1, 2, 3 ].map(iter), [ 2, 3, 4 ]);

Helper returns function constructed as this:

function ($item, $i, $list, $) {
  // $item is value of array ($list) element at index ($i)
  // Last $ argument is array of arguments passed after pattern
  with ($item) return %pattern%;
}

cmem.memos

List of cmem instances.

assert.equal(cmem(), cmem.memos[0]);

cmem.noop

Just empty function.

cmem().$calls

Registry list of function calls.

var object = { method: cmem() };
object.method(1, 2);
object.method(3, 4);

console.log(object.method.$calls);
// Output:
// [ { '$args': { '0': 1, '1': 2 },
//     '$this': { method: [Function: ctx] } },
//   { '$args': { '0': 3, '1': 4 },
//     '$this': { method: [Function: ctx] } } ]

cmem().$count

Shortcut for cmem().$calls.length.

cmem().$last

Shortcut for (fn = cmem()).$calls[fn.$calls.length - 1].

cmem().$args

Shortcut for cmem().$last.$args.

cmem().$this

Shortcut for cmem().$last.$this.

cmem().$clear()

Clears cmem instance call registry and resets counter.

var fn = cmem();
fn();
assert.equal(fn.$count, 1);
fn.$clear();
assert.equal(fn.$count, 0);

cmem().$fn( [ fn ] )

Switches function to passed one. If nothing passed cmem(fn) will be used.

var inc = cmem(function (a) { return a + 1; });
assert.equal(inc(1), 2);

inc.$fn(function (a) { return a + 2; });
assert.equal(inc(1), 3);

inc.$fn();
assert.equal(inc(1), 2);

cmem().$unit( value )

Switches function to one that returns passed value.

Shortcut to cmem().$fn(cmem.unit(value)).

var inc = cmem(function (a) { return a + 1; });
assert.equal(inc(1), 2);

inc.$unit(1);
assert.equal(inc(1), 1);

inc.$unit(3);
assert.equal(inc(1), 3);

inc.$fn();
assert.equal(inc(1), 2);

cmem().$map( patternOrFunction, [ arg ], ... )

Array map method shortcut for function calls.

var multiplier = 3;

var fn = cmem();
fn(1, 2);
fn(2, 1);
fn(2, 2);

var map1 = fn.$calls.map(function (item) {
  return (item.$args[0] + item.$args[1]) * multiplier;
});

var map2 = fn.$map('($args[0] + $args[1]) * $[0]', multiplier);

assert.deepEqual(map1, map2);

cmem().$filter( patternOrFunction, [ arg ], ... )

Array filter method shortcut for function calls.

var fn = cmem();
var object1 = { method: fn };
var object2 = { method: fn };

object1.method(1);
object2.method(2);
object1.method(3);

assert.equal(fn.$filter('$this === $[0]', object1).length, 2);
assert.equal(fn.$filter('$this === $[0]', object2).length, 1);

// Same as:
assert.equal(fn.$calls.filter(function (item) {
  return item.$this === object1;
}).length, 2);

assert.equal(fn.$calls.filter(function (item) {
  return item.$this === object2;
}).length, 1);

cmem().$select( filterPatternOrFunction, mapPatternOrFunction, [ arg ], ... )

Combines $filter and $map methods.

var fn = cmem();
var object1 = { method: fn };
var object2 = { method: fn };

object1.method(1);
object2.method(2);
object1.method(3);

assert.deepEqual(fn.$select('$this === $[0]', '$args[0]', object1), [ 1, 3 ]);
assert.deepEqual(fn.$select('$this === $[0]', '$args[0]', object2), [ 2 ]);

// Same as:
assert.deepEqual(fn.$calls.filter(function (item) {
  return item.$this === object1;
}).map(function (item) {
  return item.$args[0];
}), [ 1, 3 ]);

assert.deepEqual(fn.$calls.filter(function (item) {
  return item.$this === object2;
}).map(function (item) {
  return item.$args[0];
}), [ 2 ]);

License

MIT

neytema/cmem