brandonweis

// 实现一个浏览器的前进、后退与前进网址的功能


current -> a

backup -> c, b


class Navigator {

brandonweis

/*
  Made by Elly Loel - https://ellyloel.com/
  With inspiration from:
    - Josh W Comeau - https://courses.joshwcomeau.com/css-for-js/treasure-trove/010-global-styles/
    - Andy Bell - https://piccalil.li/blog/a-modern-css-reset/
    - Adam Argyle - https://unpkg.com/open-props@1.3.16/normalize.min.css / https://codepen.io/argyleink/pen/KKvRORE

  Notes:
    - `:where()` is used to lower specificity for easy overriding.
*/

brandonweis

const error_handler = (property) => {
  throw new Error(`Error: ${property} is required!`);
}

const monitor_roads = (car=error_handler('Car'), speed=error_handler('Speed')) => {
  console.log(`Your ${car} was going at a speed of ${speed}mph.`);
}

monitor_roads('Ferrari', 240); // Your Ferrari was going at a speed of 240mph.
monitor_roads('Ferrari'); // Error: Speed is required!

brandonweis

/*
# Coding exercise

Implement the array reduce function (including tests)

var arr1 = [1,2,3,4];
arr1.reduce((acc, value) => acc + value, 0); // 10

Extension: avoid using loops (use recursion)
*/

brandonweis

/*
You have 2 different applications running in the webpage, one with the cart count and another is a list of products. When you add click on "Add to cart" in the project, the cart count needs to get updated. 

Implement a eventBus / pub/Sub solution to allow communication between the two applications.

Write tests to cover common use cases.
*/

const EventBus = () => {
  const listeners = {}

brandonweis

// promise error handling
function fetchAndUpdatePosts() {
  fetchPosts()
    .then((posts) => {
      updatePosts(posts)
        .catch((err) => {
          console.log('error in updating posts');
        });
    })
    .catch(() => {

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const caughtFunction = () => {
    try {
        blarg;
    } catch (e) {
        throw new Error('Ghaaa!');
    }
}

const throwingFunction = () => {
    throw new Error('Ghaaa!');

brandonweis

/*
Implement the array flat function. 
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/flat
Creates a new array with all sub-array elements concatenated into it recursively up to the specified depth.

var arr1 = [1, 2, [3, 4]]; 
arr1.flat(); // [1, 2, 3, 4]

var arr2 = [1, 2, [3, 4, [5, 6]]]; 
arr2.flat(); // [1, 2, 3, 4, [5, 6]] 

brandonweis

export const cancellablePromise = promise => {
  let isCanceled = false;

  const wrappedPromise = new Promise((resolve, reject) => {
    promise.then(
      value => (isCanceled ? reject({ isCanceled, value }) : resolve(value)),
      error => reject({ isCanceled, error }),
    );
  });

brandonweis

import React, { PropTypes } from 'react';

const Repeater = function(props, context) {
    const count = props.count || 1;
    const temp = [];
    for (let i = 0; i < count; i++) {
        temp.push(props.children);
    }
    console.log(temp);