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Install1yarn add --dev jest Simple Case123456// sum.jsfunction sum (a, b) { return a + b}module.exports = sum 12345678// sum.test.jsconst test = require('jest')const expect = require('expect')const sum = require('./sum')test('adds 1 + 2 to equals 3', () => { expect(sum(1, 2).toBe(3))}) With Babel1yarn add --dev babel-jest 12345678910// .babelrc{ "presets": [ [ "env", { "targets": ...

Currently a ‘function-like’ import() module loading syntax proposal is on the way into ECMAScript. The ES6 Defines import() as method to load ES6 modules dynamically onruntime. Webpack treats import() as a split-point and puts the requested module in a seperate chunk. import() takes the module name as argument and returns a Promise: import(name) => Promise 1234567function determineDate () { import('moment').then((moment) => { console.log(moment().format()) }). ...

yarn add mongoose import mongoose from 'mongoose' const db = mongoose.conenct(MONGODB_URI) 1234567891011import mongoose from 'mongoose'const db = mongoose.connect(MONGODB_URI)db.connection.on('open', () => { console.log('connected')})db.connection.on('error', (err) => { console.log(`db error: ${err}`) process.exit}) SchemaSchema defines the skeleton of minimal unit 1234567import mongoose from 'mongo ...

Configuring TypeScript CompilationTypeScript uses the file tsconfig.json to adjust project compile options 123456789101112131415"compilerOptions": { "module": "commonjs", "target": "es6", "noImplicityAny": true, "moduleResolution": "node", "sourceMap": true, "outDir": "dist", "baseUrl": ".", "paths": { "*": [ "node_mo ...

Dragging and dropping files from your desktop to a browser is one of the ultimate goals for web application integration, which consists of: enable file dragging and dropping onto a web page element analyze dropped files in JavaScript load and parse files on the client asynchronously upload files to the server using XMLHttpRequest2 show a graphical progress bar while the upload occurs use progressive enhancement to ensure your file upload from works in any browser The File API FileList: r ...

Original Both map() and flatMap() take a function f as a parameter that controls how an input Array is translated to an output Array: With map(), each input Array element is translated to exactly one output element, aka, f returns a single value With flatMap(), each input Array element is translated to zero or more output elements, aka, f returns an Array of values. An smiple implementation of flatMap: 123456789101112function flatMap (arr, mapFunc) { const result = [] for (const [inde ...

babel-preset-env is a new preset which let you specify an environment and automatically enables the necessary plugins. At the moment, several presets let you determine what features Babel should support: babel-preset-es2015, babel-preset-es2016, etc: incrementally support various versions of ECMAScript. babel-preset-es2015 transpiles what’s new in ES6 to ES5, babel-preset-es2016 transpiles what’s new in ES7 to ES6. babel-preset-latest: supports all features that are either part of an ECMAScrip ...

The babel-polyfill and babel-runtime modules are sued to serve the same function in two different ways. Both modules ultimately serve to emulate an ES6 environment. Both babel-polyfill and babel-runtime emulate an ES6 environment with two things: a slew of polyfills as provided by core-js complete generator runtime babel-polyfill accomplishes this task by assigning methods on the global or on native type prototypes which means that once required, as far as the javascript runtime you’re using ...

This plugin is recommended in a library/tool Note: Instance methods such as 'foobar'.includes('foo') will not work since that would require modification of existing built-ins(Use babel-polyfill for that) Babel uses very small helpers for common functions such as _extend. By default this will be added to every file that requires it. This duplication is sometimes unnecessary, especially when your application is spread out over multiple files. This is where the transform-runtime p ...

Original An basic Avatar Component: 12345class Avatar extends React.Component { render () { return <img src={this.props.url} /> }} And its functional component style is: 1const Avatar = ({ url }) => <img src={url} /> As you can see, it’s just a simple js function returning an element. React still does a lot of stuff on functional components that, by nature, will never be used. But we can skip React internals for these functi ...

12345678910body { background: url(...) /* image */ top center / 200px 200px /* position / size */ no-repeat /* repeat */ fixed /* attachment */ padding-box /* origin */ content-box /* clip */ red; /* color */}

Original IntroductionCSS Grid Layout (aka ‘Grid’), is a two-dimensional grid-based layout system that aims to do nothing less than completely change the way we design grid-based user interfaces. TerminologyGrid ContainerThe element on which display: grid is applied. It’s the direct parent of all the grid items. In this example container is the grid container. 12345<div class="container"> <div class="item item-1"></div> <div class="item item-2" ...

Original Basic Syntax of SCP1scp source_file_name username@destination_host:destination_folder Provider the detail information of SCP process using -v parameterBaisc SCP command without parameter will copy the files in background. User will see nothing unless the process is done or something error appears. You can use -v parameter to print debug information into screen. 12# verbosescp -v source_file_name username@destination_host:destination_folder Provider modification times, access times, an ...

CreateYou can create an Observable from scratch by using the Create operator. You pass this operator a function that accepts the observer as its parameter. Write this function so that it behaves as an Observable – by calling the observer’s onNext, onError, and onCompleted methods appropraitely. A well-formed finite Observable must attempt to call either the observer’s onCompleted method exactly once or its onError method exactly once, and must not thereafter attempt to call any of the observer’s ...

ClusterA single instance of Node.js runs in a single tread. To take advantage of multi-core systems the user will sometimes want to launch a cluster of Node.js processes to handle the load. The cluster module allows you to easily create child processes that all share server port. 1234567891011121314151617181920212223242526const cluster = require('cluster')const http = require('http')const numCPUs = require('os').cpus().lengthif (cluster.isMaster) { console.log ...

alias axios.request(config) axios.get(url[, config]) axios.delete(url[, config]) axios.head(url[, config]) axios.options(url[, config]) axios.post(url[, data[, config]]) axios.put(url[, data[, config]]) axios.patch(url[, data[, config]]) Config Optionsurl is required, and get is the default method 12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758{ url: 'string', method: 'get', baseUrl: 'https://some-domai ...

devServer.proxy: object Proxying some URLs can be useful when you have a separate API backend development server and you want to send API requests on the same domain. The dev-server makes use of the powerful http-proxy-middleware package. With a backend on localhost:3000, you can use this to enable proxying: 123proxy: { '/api': 'http://localhost:3000'} A request to /api/users will now proxy to the request to http://localhost:3000/api/users If you don’t ...

HashRouterVersion 4 of React-Router seperate top level router element for the different history type. If you’re using version 4 you should be able to replace <Router hisotry={hashHistory}> with <HashRouter> Multiple Routes at same URL123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172import React from 'react'import { BrowserRouter as Router, Route, Link,} from 're ...

d3-arrayarray methods built-in to JavaScript array.pop => popped element array.push => array.length array.reverse => change the array array.shift => shifted element array.unshift => array.length array.sort => change the array array.splice => change the array array.concat => new Array array.join => new String array.slice => new Array array.indexOf => number array.lastIndexOf => number array.fitler => new Array array.forEach => undefined arra ...

I had encountered a problem using node-inspector with info cb(error, NM[0].ref); Cannot read property ‘ref’ of undefined And one method to resolve it is to modify the packagge Same issue with node v6.5.0 can be solved like this : Edit …\node_modules\node-inspector\lib\InjectorClient.js file at line 111 if(NM.length > 0) cb(error, NM[0].ref); It works which is hack, and another method is without side-effect use the local node-inspector hope it helps