| function times(str, n) { | |
| if (n == 0) { | |
| return ''; | |
| } | |
| if (n == 1) { | |
| return str; | |
| } else { | |
| return str + times(str, n - 1); | |
| } |
Picking the right architecture = Picking the right battles + Managing trade-offs
| // Async Await is syntactic sugar over promises | |
| // They are not a complete replacement as you still need to construct Promise objects | |
| // and methods like Promise.all([]) can only be done with promises | |
| const myFetch1 = () => { | |
| return new Promise((resolve, reject) => { | |
| setTimeout(() => { | |
| if (Math.random() > 0.05) { // change this to trigger the catch blocks | |
| resolve('foo') | |
| } else { |
| function InvalidRequestError(statusCode, message) { | |
| const defaultMessage = 'invalid request, status code ' + statusCode; | |
| this.name = 'InvalidRequestError'; | |
| this.message = message || defaultMessage; | |
| this.stack = (new Error()).stack; | |
| } | |
| InvalidRequestError.prototype = Object.create(Error.prototype); | |
| InvalidRequestError.prototype.constructor = InvalidRequestError; |
| // simplified promise implementation for learning purposes | |
| // https://levelup.gitconnected.com/understand-javascript-promises-by-building-a-promise-from-scratch-84c0fd855720 | |
| class MyPromise { | |
| constructor(promiseCallback) { | |
| this.promiseChain = [] | |
| this.handleError = () => {} | |
| // bind this as onResolve and onReject callbacks are passed into the promise callback | |
| this.onResolve = this.onResolve.bind(this) |
| // Lazy evaluation in javascript | |
| // call by name: lazily evaluate the arguments passed into the function | |
| // call by value: eagerly evaluate the arguments passed into the function | |
| // call by need: memoized version of call by name | |
| // memoization: avoid recomputation for the same inputs by caching the results | |
| // | |
| // Javascript by default uses call by value, however by using Object.defineProperty(), | |
| // lazy evaluation in javascript object properties can be performed | |
| // | |
| // e.g. an infinite data structure - the stream, can only exist with lazy evaluation (else infinite recursion) |
| <!DOCTYPE html> | |
| <html lang="en"> | |
| <head> | |
| <title>React::Inline</title> | |
| <meta charset="utf-8"> | |
| <meta name="viewport" content="width=device-width, initial-scale=1"> | |
| <link rel="stylesheet" href="https://unpkg.com/purecss@1.0.0/build/pure-min.css" integrity="sha384-nn4HPE8lTHyVtfCBi5yW9d20FjT8BJwUXyWZT9InLYax14RDjBj46LmSztkmNP9w" crossorigin="anonymous"> | |
| </head> | |
| <body> | |
| <div id="app"></div> |
| const http = require('http') | |
| const HOSTNAME = 'localhost' | |
| const PORT = 3000 | |
| const client = () => { | |
| const bodyString = JSON.stringify({ | |
| username: 'foobar', | |
| password: 'Password1' | |
| }) |
| // HigherOrderComponentExample | |
| import React, { Component } from 'react' | |
| // https://gist.github.com/sebmarkbage/ef0bf1f338a7182b6775 | |
| // will augment component to include a loading wheel | |
| // curried Higher order function | |
| const LoaderHOC = (propName) => (WrappedComponent) => { | |
| return class LoaderHOC extends Component { | |
| isEmpty(prop) { | |
| return ( |
| // example inspired by https://gist.github.com/chantastic/fc9e3853464dffdb1e3c | |
| /* ------------- V0 ------------ | |
| * Here you have complex component that is hard to test | |
| * and difficult to understand, extend and maintain | |
| */ | |
| import React from 'react' | |
| class CommentList extends React.Component { | |
| constructor() { |