prof3ssorSt3v3 · September 13, 2021 21:53
diff --git a/app.mjs b/app.mjs
 /**
 * Currying vs Partial Application
 * Closures
 *   A function which returns a function that
 *   can has access to the returned function's scope.
 *   function example(param){
 *     let a = 123;
 *     return function(otherParam){
 *       //both param and otherParam and a are available here
 *     }
 *   }
 *
 * Partial Application
 *   Uses closures.
 *   Returned function is partially applied to a new value,
 *   meaning that the value passed to the original function
 *   is already attached to the returned `partially applied` function
 *
 * Currying
 *   The process of taking a multiple argument function and
 *   breaking it up into a series of single argument partially
 *   applied functions.
 */
 const log = console.log;

 //Simple demo - the things we would want to curry
 function bakeChocolateCupcakeWithVanilla(cakeType, cakeFlavor, icingType) {
  return `Made a ${cakeFlavour} ${cakeType} with ${icingType} icing.`;
 }
 function bakeVanillaCakeWithLemon(cakeType, cakeFlavor, icingType) {
  return `Made a ${cakeFlavour} ${cakeType} with ${icingType} icing.`;
 }
 //curry it
 function bake(cakeType) {
  //partially applied
  return function (cakeFlavour) {
    //partially applied
    return function (icingType) {
      return `Made a ${cakeFlavour} ${cakeType} with ${icingType} icing.`;
    };
  };
 }
 let bakeCake = bake('cake');
 let bakeCupcake = bake('cupcake');
 let bakeMuffin = bake('muffin');

 let chocCake = bakeCake('chocolate');
 let vanillaCake = bakeCake('vanilla');
 let chocCupcake = bakeCupcake('chocolate');
 let carrotMuffin = bakeMuffin('carrot');

 // log(chocCake('strawberry'));
 // log(chocCake('vanilla'));
 // log(chocCupcake('chocolate'));
 // log(chocCupcake('orange'));

 // log(bake('cake')('chocolate')('vanilla'));
 // log(bake('cupcake')('chocolate')('cherry'));
 // log(bake('muffin')('carrot')('vanilla'));

 //More realistic example
 import fetch from 'node-fetch';

 /**
 * Possible resources are posts, comments, albums, photos, todos, and users
 * @param {string} endpoint which resource to get from http://jsonplaceholder.typicode.com/
 * @returns {function} partially applied function
 */
 let jsonPlaceholder = async (endpoint) => {
  let url = `http://jsonplaceholder.typicode.com/${endpoint}`;
  let resp = await fetch(url);
  let data = await resp.json();
  return (num) => {
    return data
      .slice(0, num)
      .map((item) => {
        let label = item.name || item.title;
        return `<p>${endpoint} :: ${label}</p>`;
      })
      .join('\n');
  };
 };

 const sleep = (milliseconds) => {
  return new Promise((resolve) => setTimeout(resolve, milliseconds));
 };

 async function init() {
  let posts = await jsonPlaceholder('posts');
  let users = await jsonPlaceholder('users');

  sleep(3000).then(() => {
    //after 3 seconds this runs
    log(posts(2));
    log(users(4));
  });
 }
 init();
	/**
	* Currying vs Partial Application
	* Closures
	* A function which returns a function that
	* can has access to the returned function's scope.
	* function example(param){
	* let a = 123;
	* return function(otherParam){
	* //both param and otherParam and a are available here
	* }
	* }
	*
	* Partial Application
	* Uses closures.
	* Returned function is partially applied to a new value,
	* meaning that the value passed to the original function
	* is already attached to the returned `partially applied` function
	*
	* Currying
	* The process of taking a multiple argument function and
	* breaking it up into a series of single argument partially
	* applied functions.
	*/
	const log = console.log;

	//Simple demo - the things we would want to curry
	function bakeChocolateCupcakeWithVanilla(cakeType, cakeFlavor, icingType) {
	return `Made a ${cakeFlavour} ${cakeType} with ${icingType} icing.`;
	}
	function bakeVanillaCakeWithLemon(cakeType, cakeFlavor, icingType) {
	return `Made a ${cakeFlavour} ${cakeType} with ${icingType} icing.`;
	}
	//curry it
	function bake(cakeType) {
	//partially applied
	return function (cakeFlavour) {
	//partially applied
	return function (icingType) {
	return `Made a ${cakeFlavour} ${cakeType} with ${icingType} icing.`;
	};
	};
	}
	let bakeCake = bake('cake');
	let bakeCupcake = bake('cupcake');
	let bakeMuffin = bake('muffin');

	let chocCake = bakeCake('chocolate');
	let vanillaCake = bakeCake('vanilla');
	let chocCupcake = bakeCupcake('chocolate');
	let carrotMuffin = bakeMuffin('carrot');

	// log(chocCake('strawberry'));
	// log(chocCake('vanilla'));
	// log(chocCupcake('chocolate'));
	// log(chocCupcake('orange'));

	// log(bake('cake')('chocolate')('vanilla'));
	// log(bake('cupcake')('chocolate')('cherry'));
	// log(bake('muffin')('carrot')('vanilla'));

	//More realistic example
	import fetch from 'node-fetch';

	/**
	* Possible resources are posts, comments, albums, photos, todos, and users
	* @param {string} endpoint which resource to get from http://jsonplaceholder.typicode.com/
	* @returns {function} partially applied function
	*/
	let jsonPlaceholder = async (endpoint) => {
	let url = `http://jsonplaceholder.typicode.com/${endpoint}`;
	let resp = await fetch(url);
	let data = await resp.json();
	return (num) => {
	return data
	.slice(0, num)
	.map((item) => {
	let label = item.name \|\| item.title;
	return `<p>${endpoint} :: ${label}</p>`;
	})
	.join('\n');
	};
	};

	const sleep = (milliseconds) => {
	return new Promise((resolve) => setTimeout(resolve, milliseconds));
	};

	async function init() {
	let posts = await jsonPlaceholder('posts');
	let users = await jsonPlaceholder('users');

	sleep(3000).then(() => {
	//after 3 seconds this runs
	log(posts(2));
	log(users(4));
	});
	}
	init();