ecmascript-6

问题 This question already has an answer here : Destructuring assignment in while loop in ES6 function doesn't propogate out of loop? (1 answer) Closed 4 years ago . I am simply using es6 to reassign variables a & b. Why do I get an error if I leave the semicolon off of the a and b declaration and assignment statements? Does the parser try to pull a property out of 2 if the semicolon is left off? let b = 2[a, b]...? Works: let a = 1; let b = 2; [a, b] = [b, a] Error: let a = 1 let b = 2 [a, b] =

问题 I have an array of objects with these properties: material_no, material_name, qty. let data = [ { material_no: '1001', material_name: 'Material 1', qty: 100 }, { material_no: '1001', material_name: 'Material 1', qty: 50 }, { material_no: '1002', material_name: 'Material 2', qty: 44 }, { material_no: '1003', material_name: 'Material 3', qty: 125 }, { material_no: '1002', material_name: 'Material 2', qty: 59 }, { material_no: '1004', material_name: 'Material 4', qty: 999 }, { material_no: '1005

问题 I'm learning React and now i'm trying do a get resquest and list with map but when I run this code they come up with this error "Unhandled Rejection (TypeError): this.state.features.map is not a function". I already search this but I'm not undertand what its going on. import React, { Component } from 'react'; import './App.css'; class App extends Component { constructor() { super(); this.state = { features: [{ id: 1, name: 'Test', count: 1 }] } } componentWillMount() { fetch("http:/

问题 I'm learning React and now i'm trying do a get resquest and list with map but when I run this code they come up with this error "Unhandled Rejection (TypeError): this.state.features.map is not a function". I already search this but I'm not undertand what its going on. import React, { Component } from 'react'; import './App.css'; class App extends Component { constructor() { super(); this.state = { features: [{ id: 1, name: 'Test', count: 1 }] } } componentWillMount() { fetch("http:/

问题 I found a function I can use in a Leaflet project I’m working. The function is written is ES6 and it works great in both Firefox and Chrome. However, I need to target IE as well. In my research I found IE at present don't accept the ES6 Arrow function. I also I found if the ES6 function was converted to ES5, the function will work in IE. For days now I tried to convert the following function to ES5 but to no prevail. Some of the solutions I tried were found posted here. Can some please look

问题 I found a function I can use in a Leaflet project I’m working. The function is written is ES6 and it works great in both Firefox and Chrome. However, I need to target IE as well. In my research I found IE at present don't accept the ES6 Arrow function. I also I found if the ES6 function was converted to ES5, the function will work in IE. For days now I tried to convert the following function to ES5 but to no prevail. Some of the solutions I tried were found posted here. Can some please look

问题 I'm running into a bug where I use the spread operator to delete an object property. I tested the code in the console and it works there but I'm unclear why it's not working in my React App. Here's my other question for reference and now I'm using the accepted answer's code line by line: https://stackoverflow.com/questions/64000577/rest-operator-to-omit-properties . I followed the entire debug path in the Source tab using breakpoint. I get inside the if statement and when it's time to

问题 I have some questions regarding MutationObserver and ways to improve it. From that answer: Use debounce or a similar technique e.g. accumulate mutations in an outer array and schedule a run via setTimeout / requestIdleCallback / requestAnimationFrame: const queue = []; const mo = new MutationObserver(mutations => { if (!queue.length) requestAnimationFrame(process); queue.push(mutations); }); function process() { for (const mutations of queue) { // .......... } queue.length = 0; } Is it

问题 I have following problem: I intend to fetch data via web API and on its basis, React Native will render it using FlatList. It will use a child component, in this case (Checkbox). So, there will be multiple checboxes. How can I create and update state of these checboxes when I don't know their count and then pass their state to child component? const data = [{ id:0, product:"A" price:30 }, { id:1, product:"B" price:20 }, { id:1, product:"C" price:10 }] (I am scratching my head) 回答1: Output:

问题 With traditional JavaScript namespacing techniques I am able to create a nested logical grouping, even over multiple files. How should I replace that with ES modules alias import. Consider the case where I want all my code in a CompanyName namespace, then group by products and within a product I may have a group of shared functions and these could be grouped by topic (very common in many languages like Java, C# etc.). F.e. CompanyName = { ProductName1: { Shared: { Database: {