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Haskell like monad in ES6
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| var UpperCase = value => { | |
| if(!value) return value; | |
| return value.toUpperCase(); | |
| } | |
| var LowerCase = value => { | |
| if(!value) return value; | |
| return value.toLowerCase(); | |
| } | |
| // Identity monad | |
| Monad.create( | |
| Monad.create('hello').bind(UpperCase) | |
| ).bind(LowerCase) // => hello | |
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| let list = ['a','b']; | |
| var beforeAdd = (obj, array) => { | |
| var result = []; | |
| if(!(obj instanceof Array)) obj = [obj]; | |
| obj.forEach(function(item) { | |
| var tmp = array.map(function(words) { | |
| return words + '-' + item; | |
| }); | |
| result = result.concat(tmp); | |
| }); | |
| return result; | |
| } | |
| var afterAdd = (obj, array) => { | |
| var result = []; | |
| if(!(obj instanceof Array)) obj = [obj]; | |
| obj.forEach(function(item) { | |
| var tmp = array.map(function(words) { | |
| return item + '-' + words; | |
| }); | |
| result = result.concat(tmp); | |
| }); | |
| return result; | |
| } | |
| // List | |
| Monad.create( | |
| Monad.create('test').bind(beforeAdd, [list]) | |
| ).bind(afterAdd, [list]); // => [ 'a-test-a', 'a-test-b', 'b-test-a', 'b-test-b' ] |
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| var UpperCase = value => { | |
| if(!value) return value; | |
| return value.toUpperCase(); | |
| } | |
| var LowerCase = value => { | |
| if(!value) return value; | |
| return value.toLowerCase(); | |
| } | |
| // Maybe | |
| Monad.create( | |
| Monad.create(null).bind(UpperCase) | |
| ).bind(LowerCase); // => null |
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| 'use strict'; | |
| class Monad { | |
| constructor(value) { | |
| if (typeof modifier === 'function') { | |
| this._modifier = value; | |
| } else { | |
| this._value = value; | |
| } | |
| } | |
| static create(func) { | |
| return new Monad(func); | |
| } | |
| value() { | |
| if(this._value === undefined) return undefined; | |
| return this._value; | |
| } | |
| bind(func, args) { | |
| return func.apply(undefined, [this.value()].concat(Array.prototype.slice.apply(args || []))); | |
| } | |
| } |
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| <!DOCTYPE html> | |
| <html> | |
| <head> | |
| <meta charset="utf-8"> | |
| <title>QUnit Example</title> | |
| <link rel="stylesheet" href="https://code.jquery.com/qunit/qunit-1.19.0.css"> | |
| </head> | |
| <body> | |
| <div id="qunit"></div> | |
| <div id="qunit-fixture"></div> | |
| <script src="https://code.jquery.com/qunit/qunit-1.19.0.js"></script> | |
| <script src="es6.js"></script> | |
| <script src="test.js"></script> | |
| </body> | |
| </html> |
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| QUnit.test( '`return x >>= f` should be equal `f a`', function( assert ) { | |
| var f = function(a) { return a * 2; } | |
| var left = Monad.create(1).bind(f); | |
| var right = f(1); | |
| assert.equal(left, right, 'left, right is equal'); | |
| }); | |
| QUnit.test('`m >>= return` should be equal `m`', function( assert ) { | |
| var left = Monad.create(Monad.create().value()); | |
| var right = Monad.create(); | |
| assert.deepEqual(left, right, 'left, right is equal'); | |
| }); | |
| QUnit.test('`(m >>= f) >>= g` should be equal `m >>= (x -> f x >>= g`', function( assert ) { | |
| var f = function f(num) { | |
| return num + 1; | |
| } | |
| var g = function(num) { | |
| return num * 2; | |
| } | |
| var left = Monad.create( Monad.create(1).bind(f) ).bind(g); | |
| var right = Monad.create( Monad.create(f(1)).bind(g) ).value(); | |
| assert.deepEqual(left, right, 'left, right is equal'); | |
| }); |
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