Monadify

Make your javascript code cleaner and more expressive with the power of monads and functional programming.

Features

• Makes your code more expressive by using a form of function chaining, instead of wrapping the input inside multiple function calls.
• Fail the way you want, by passing custom error handling functions so that you don't have to abuse try and catch statements.
• Does not mutate objects, creates a new cloned object on each instantiation, to prevent bug spewing mutations on the original object.
• Now with support for lodash/underscore - Simply use the popular utility library you want, and gain all the functionality it provides.

Install

$ npm install --save monadify

Usage

var Monadify = require('monadify'),
  n = 1;
 
function add(n){
  return n + 1;
}
 
//The old way
console.log(add(add(add(n))));
//=> 4
 
//With Monadify
var nMonad = Monadify(n)
  .bind(add)
  .bind(add)
  .bind(add)
  .send(console.log);
//=> 4
 
//To return the result
var result = nMonad.value();
console.log(result);
//=> 4

Documentation

• Constructor
• bind
• send
• value
• Lodash/underscore support

Monadify(input, [errorHandler])

Returns a mutation (monad) of the input argument. Optional errorHandler function, which gets called if an error is thrown somewhere down the function chain.

Arguments

• input - The input for the monad. Objects given as input are cloned, to prevent mutation.
• errorHandler(error) - Callback function to handle error thrown anywhere in the function chain.

Examples

var nMonad = Monadify(1);
 
var obj = {},
 objMonad = Monadify(obj);
 
//Objects passed to the constructor are cloned, which means any changes applied to 'obj' are not passed on to objMonad.
obj.a = 'a';
objMonad.send(console.log);
//=> {}

Error handling

Defaults to throw new Error(e);. Calls the errorHandler function, if present.

var nMonad = Monadify(1, console.log);
// Logs any errors to the console, instead of throwing an error.
 
var notAFunction = null,
 
  identity = function(n){
    return n;
  };
 
nMonad.bind(identity)
  .bind(notAFunction)
  .bind(identity);
 
//=> [TypeError: object is not a function]

bind(bindingFunction)

binds the given function to the current state of the input. Mutates the input into the returned value of bindingFunction.

Arguments

• bindingFunction(input) - Function to be bound to the current state of the input.

Examples

var nMonad = Monadify(2);
 
nMonad.bind( n => n*3);
//current state of nMonad is 6
nMonad.send(console.log);
//=> 6
 
//Monads bound to console.log will subsequently return undefined, since the console.log function has no return value
nMonad.bind(console.log);
//=> 6
// current state of nMonad is undefined
nMonad.send(console.log);
//=> undefined

send(sentToFunction)

sends the current state of input to the given function. Does not affect or mutate the input, and retains input state before sending to sentToFunction.

Arguments

• sentToFunction(input) - Function to which the current state of input is passed as an argument. Return value is disregarded.

Examples

var nMonad = Monadify(2);
 
nMonad.send( n => n*3);
//current state of nMonad is still 2
nMonad.send(console.log);
//=> 2
 
//Monads bound to console.log will subsequently return undefined, since the console.log function has no return value
nMonad.send(console.log);
//=> 2
// current state of nMonad is 2
nMonad.send(console.log);
//=> undefined

value()

Returns the current state of input.

Examples

var nMonad = Monadify(2);
nMonad.bind( n => n*3);
 
var n = nMonad.value();
//value of n is 6
console.log(n);
//=> 6

Lodash/underscore support*

Monadify supports the use of external utility libraries like lodash. It extends their functionality to provide for a great and expressive new way to write code. Lodash functions of the form _.someFunction(operand, argument) can be used with Monadify as someMonad.someFunction(argument).value() (see example).

* This feature is still in development. Contributions are welcome :)

Examples

var Monadify = require('monadify'),
  _ = require('lodash');
 
Monadify.use(_);
 
var nMonad = Monadify([1,2,3]);
 
nMonad.map(addOne)  //Native lodash function => [2,3,4]
  .max()  //Native lodash function => 4
  .bind(addOne) // Monadify bind function => 5
  .value(); // => 5
 
 
function addOne(n){
  return n + 1;
};

License

MIT © Soham Kamani