ecmascript-6

问题 Angular2 has very useful promises error catching mechanism for chained promises. Yet, the usual case (at least for me) is that of promises called from within the resolve handler of the previous one. This is due to the need to process information prior to starting the next promise. For example: this.d( "facebookOAuthLogin() - starts" ); this.fbProvider.login().then( ( loginResponse: { status: string, authResponse: any, accessToken: string, expiresIn: string, session_key: string, sig: string,

问题 How can a child access its parent's props? For instance, A parent component - footer.jsx: import React from 'react'; import $ from 'jquery'; import NavItem from './nav-item'; class Footer extends React.Component { constructor(props) { super(props); this.state = { publicUrl: null, currentUrl: null, navitems: [], }; } // Then fetch the data using $.getJSON(): componentDidMount() { this.serverRequest = $.getJSON(this.props.source, function (result) { this.setState({ currentUrl: window.location

问题 Angular2 has very useful promises error catching mechanism for chained promises. Yet, the usual case (at least for me) is that of promises called from within the resolve handler of the previous one. This is due to the need to process information prior to starting the next promise. For example: this.d( "facebookOAuthLogin() - starts" ); this.fbProvider.login().then( ( loginResponse: { status: string, authResponse: any, accessToken: string, expiresIn: string, session_key: string, sig: string,

问题 I am working on an app and I am using bottomTabNavigator but in mean time I am getting this warning! ( Look like you're passing an inline function for 'Component' prop for the screen 'Feed' (e.g component={()=><SomeComponent/>)). Passing an inline function will cause the component state to be lost on re-render and cause perf issue since it's re-created every render. You can pass the function as children to 'Screen' instead to achieve the desired behaviour. I know I am doing something wrong

问题 I have already gone through the thread Any difference between await Promise.all() and multiple await?, so I am clear about Promise.all and multiple awaits. Still, I am not very clear about the below 2 scenarios. In Case 1 why does it execute sequentially (takes 10s) whereas in Case 2 it executes in parallel (takes 4s)? Case 1: function promiseWait(time) { return new Promise((resolve, reject) => { setTimeout(() => { resolve(true); }, time); }); } async function test1() { var t0 = performance

问题 I have React app and a file where I want to store things related to api. const proxy = require('http-proxy-middleware'); const path = require('path'); //..... const targetApi = (objectWithUrlEntries) => { Object.keys(objectWithUrlEntries).forEach((key) => { objectWithUrlEntries[key] = path.join('/api/', objectWithUrlEntries[key]); }); }; module.exports.proxyExpressCalls = proxyExpressCalls; module.exports.devServerProxyConfig = devServerProxyConfig; module.exports.targetApi = targetApi; Some

问题 How to reuse some existing ES6 classes in Vue Js. Have a class which has a variable being updated by observable. class A { public a: string; someobservable.subscribe((a) =>{ this.a = a; }) } In vue.JS have created the object of this class. Sample how property is been used: created: { objA = new A(); } methods: { getA() { if(this.objA !== undefined){ return objA.a; } } } and in vue template: <div>{{getA()}}</div> The value in template gets out of sync with value of variable in class. Is there

问题 How to reuse some existing ES6 classes in Vue Js. Have a class which has a variable being updated by observable. class A { public a: string; someobservable.subscribe((a) =>{ this.a = a; }) } In vue.JS have created the object of this class. Sample how property is been used: created: { objA = new A(); } methods: { getA() { if(this.objA !== undefined){ return objA.a; } } } and in vue template: <div>{{getA()}}</div> The value in template gets out of sync with value of variable in class. Is there

问题 let updateTimer: number; export function Timer() { const [count, setCount] = React.useState<number>(0); const [messages, setMessages] = React.useState<string[]>([]); const start = () => { updateTimer = setInterval(() => { const m = [...messages]; m.push("called"); setMessages(m); setCount(count + 1); }, 1000); }; const stop = () => { clearInterval(updateTimer); }; return ( <> <div>{count}</div> <button onClick={start}>Start</button> <button onClick={stop}>Stop</button> {messages.map((message,

问题 let updateTimer: number; export function Timer() { const [count, setCount] = React.useState<number>(0); const [messages, setMessages] = React.useState<string[]>([]); const start = () => { updateTimer = setInterval(() => { const m = [...messages]; m.push("called"); setMessages(m); setCount(count + 1); }, 1000); }; const stop = () => { clearInterval(updateTimer); }; return ( <> <div>{count}</div> <button onClick={start}>Start</button> <button onClick={stop}>Stop</button> {messages.map((message,