battmanz’s gists

battmanz / mutable-state.js

Last active June 19, 2017 04:21

Capturing a mutable variable causes a function to be impure.

	let heightRequirement = 46;

	function canRide(height) {
	return height >= heightRequirement;
	}

	// Every half second, set heightRequirement to a random number between 0 and 200.
	setInterval(() => heightRequirement = Math.floor(Math.random() * 201), 500);

	const mySonsHeight = 47;

battmanz / impure-functions.js

Last active June 18, 2017 22:11

Two examples of impure functions.

	let heightRequirement = 46;

	// Impure because it relies on a mutable (reassignable) variable.
	function canRide(height) {
	return height >= heightRequirement;
	}

	// Impure because it causes a side-effect by logging to the console.
	function multiply(a, b) {
	console.log('Arguments: ', a, b);

battmanz / pure-function-example.js

Last active June 18, 2017 20:26

An example of a pure function.

battmanz / partial-application-using-bind.js

Created June 18, 2017 02:39

Partial application using function.prototype.bind

	function giveMe3(item1, item2, item3) {
	return `
	1: ${item1}
	2: ${item2}
	3: ${item3}
	`;
	}

	const giveMe2 = giveMe3.bind(null, 'rock');
	const giveMe1 = giveMe2.bind(null, 'paper');

battmanz / currying-placeholder.js

Last active June 18, 2017 02:30

Using a placeholder when calling a curried function.

	const giveMe3 = R.curry(function(item1, item2, item3) {
	return `
	1: ${item1}
	2: ${item2}
	3: ${item3}
	`;
	});

	const giveMe2 = giveMe3(R.__, R.__, 'French Hens'); // Specify the third argument.
	const giveMe1 = giveMe2('Partridge in a Pear Tree'); // This will go in the first slot.

battmanz / fancy-currying.js

Last active June 16, 2017 02:36

Demonstrates currying using Ramda

	function dot(vector1, vector2) {
	return vector1.reduce((sum, element, index) => sum += element * vector2[index], 0);
	}

	const v1 = [1, 3, -5];
	const v2 = [4, -2, -1];

	// Use Ramda to do the currying for us!
	const curriedDot = R.curry(dot);

battmanz / manual-currying.js

Created June 16, 2017 02:16

Manually creating a curried version of the dot product function.

	function curriedDot(vector1) {
	return function(vector2) {
	return vector1.reduce((sum, element, index) => sum += element * vector2[index], 0);
	}
	}

	// Taking the dot product of any vector with [1, 1, 1]
	// is equivalent to summing up the elements of the other vector.
	const sumElements = curriedDot([1, 1, 1]);

battmanz / dot-product.js

Last active June 16, 2017 02:13

A function that computes the dot product of two vectors.

	function dot(vector1, vector2) {
	return vector1.reduce((sum, element, index) => sum += element * vector2[index], 0);
	}

	const v1 = [1, 3, -5];
	const v2 = [4, -2, -1];

	console.log(dot(v1, v2)); // 1(4) + 3(-2) + (-5)(-1) = 4 - 6 + 5 = 3

battmanz / composing-higher-order-functions.js

Created June 15, 2017 03:48

Demonstrates a pure functional approach to composing higher-order functions.

	const vehicles = [
	{ make: 'Honda', model: 'CR-V', type: 'suv', price: 24045 },
	{ make: 'Honda', model: 'Accord', type: 'sedan', price: 22455 },
	{ make: 'Mazda', model: 'Mazda 6', type: 'sedan', price: 24195 },
	{ make: 'Mazda', model: 'CX-9', type: 'suv', price: 31520 },
	{ make: 'Toyota', model: '4Runner', type: 'suv', price: 34210 },
	{ make: 'Toyota', model: 'Sequoia', type: 'suv', price: 45560 },
	{ make: 'Toyota', model: 'Tacoma', type: 'truck', price: 24320 },
	{ make: 'Ford', model: 'F-150', type: 'truck', price: 27110 },
	{ make: 'Ford', model: 'Fusion', type: 'sedan', price: 22120 },

battmanz / built-in-higher-order-functions.js

Created June 15, 2017 02:50

Demonstrates the use of built-in higher-order functions.

	const vehicles = [
	{ make: 'Honda', model: 'CR-V', type: 'suv', price: 24045 },
	{ make: 'Honda', model: 'Accord', type: 'sedan', price: 22455 },
	{ make: 'Mazda', model: 'Mazda 6', type: 'sedan', price: 24195 },
	{ make: 'Mazda', model: 'CX-9', type: 'suv', price: 31520 },
	{ make: 'Toyota', model: '4Runner', type: 'suv', price: 34210 },
	{ make: 'Toyota', model: 'Sequoia', type: 'suv', price: 45560 },
	{ make: 'Toyota', model: 'Tacoma', type: 'truck', price: 24320 },
	{ make: 'Ford', model: 'F-150', type: 'truck', price: 27110 },
	{ make: 'Ford', model: 'Fusion', type: 'sedan', price: 22120 },

Matt Banz battmanz