Stefan Frede stefanfrede

Hi. I’m Stefan, a front-end developer from Germany.

stefanfrede / deepmapping_recipe.js

Created August 23, 2016 06:08

Working with arrays that represent trees.

	const deepMapWith = (fn) =>
	function innerdeepMapWith (tree) {
	return Array.prototype.map.call(tree, (element) =>
	Array.isArray(element)
	? innerdeepMapWith(element)
	: fn(element)
	);
	}

	/**

stefanfrede / pluckwith_recipe.js

Created August 22, 2016 05:23

Combine the mapWith and the getWith recipe.

	const pluckWith = (attr) => mapWith(getWith(attr));

	// or even better

	const pluckWith = compose(mapWith, getWith);

	/**
	* Example
	*/
	const inventories = [

stefanfrede / getwith_recipe.js

Created August 20, 2016 06:03

getWith takes the name of an attribute and returns a function that extracts the value of that attribute from an object.

	const getWith = (attr) => (object) => object[attr]

	/**
	* Examples:
	*/
	const inventory = {
	apples: 0,
	oranges: 144,
	eggs: 36
	};

stefanfrede / memoized_recipe.js

Created August 19, 2016 06:28

Use a lookup table for recursive functions to look up results to avoid recalculation

	const memoized = (fn) => {
	const lookupTable = {};

	return function (...args) {
	const key = JSON.stringify(this, args);

	return lookupTable[key] \|\| (lookupTable[key] = fn.apply(this, args));
	}
	}

stefanfrede / object_assign_recipe.js

Created August 3, 2016 05:28

Extend objects by assigning properties.

	// Copy an object by extending an empty object:
	Object.assign({}, {
	apples: 12,
	oranges: 12
	})
	//=> { apples: 12, oranges: 12 }

	// Extend one object with another:
	const inventory = {
	apples: 12,

stefanfrede / flipandcurry_recipe.js

Created August 3, 2016 05:22

flipAndCurry is a function that takes a function as argument, “flips” the order of arguments around, and then curries it.

	const flipAndCurry = (fn) =>
	(first) => (second) => fn(second, first);

	// Example:
	// https://gist.github.com/stefanfrede/596597d8b544de08491364eab20053c6
	const mapWith = flipAndCurry(map);

	// flipAndCurry throws the current context away, so it can’t be used to flip methods.
	// A small alteration gets the job done:
	const flipAndCurry = (fn) =>

stefanfrede / mapwith_recipe.js

Created August 3, 2016 05:09

mapWith is a function that wraps around map and turns any other function into a mapper.

	const mapWith = (fn) => (list) => list.map(fn);

	// Example:
	const squaresOf = mapWith(n => n * n);

	squaresOf([1, 2, 3, 4, 5])
	//=> [1, 4, 9, 16, 25]

stefanfrede / pipeline_combinator_recipe.js

Created June 27, 2016 05:32

Compose functions in data flow.

	const pipeline = (...fns) =>
	(value) =>
	fns.reduce((acc, fn) => fn(acc), value);

	// Given:

	const addOne = (number) => number + 1;

	const doubleOf = (number) => number * 2;

stefanfrede / variadic_compose_combinator_recipe.js

Created June 27, 2016 05:28

The B Combinator, or (variadic) compose.

	const compose = (a, ...rest) =>
	rest.length === 0
	? a
	: (c) => a(compose(...rest)(c))

	// Given:

	const addOne = (number) => number + 1;

	const doubleOf = (number) => number * 2;

stefanfrede / compose_combinator_recipe.js

Created June 27, 2016 05:14

The B Combinator, or compose.

	const compose = (a, b) =>
	(c) => a(b(c))

	// Given:

	const addOne = (number) => number + 1;

	const doubleOf = (number) => number * 2;

	// Instead of: