JUnit 5 aims to adapt the Java 8 style of coding and to be more robust and flexible than JUnit 4. In this post, JUnit 5 vs JUnit 4, we will focus on some major differences between JUnit 4 and JUnit 5. 1. Read more…
export const NumberContext = React.createContext(); function App() { const [foo, changeFoo] = useState('foo') return ( <NumberContext.Provider value={{ foo, changeFoo }}> <TheButton /> <Display /> </NumberContext.Provider> ); } function TheButton() { const { changeFoo } = useContext(NumberContext) return ( <button onClick={() Read more…
<div class="box"> <img src="upimg/comm.png"/> </div> <div class="box"> <img src="upimg/comm1.png"/> </div> <div class="box"> <img src="upimg/comm2.png"/> </div> .box{ width: 100%; margin: 20px auto; background: skyblue; position: relative; padding-bottom: 56%; // change this overflow: hidden; } .box>img{ width: 100%; position: absolute; top: 0; Read more…
In my project, I jumped to another page before the web request was returned and found that the console reported an error: Warning: Can’t perform a React state update on an unmounted component. This is a no-op, but it indicates Read more…
First of all, setState has two ways of passing parameters: Pass the new value directly: setState(options) const [state, setState] = useState(0); setState(state + 1); Pass in the callback function: setState(callBack) const [state, setState] = useState(0); setState((prevState) => prevState + 1); Read more…
SUBSTRING_INDEX(str, delim, count) str: the string to be split. delim: the delimiter. count: the position of the delimiter. A positive number means extract from left to right, a negative number means extract from right to left. For example: SELECT SUBSTRING_INDEX('100-200-300-400', Read more…
When using mybatis as a persistence layer, insert, update, delete, sql statements do not return the primary key of the record being operated on by default, but rather the number of records being operated on. When we want to get Read more…
The purpose of a sticky footer is that it “sticks” to the bottom of the browser window. But not always, if there is enough content on the page to push the footer lower, it still does that. But if the Read more…
When Prettier is used in conjunction with ESLint, ESlint detects the crlf and cr differences between the code runtime and the project creator to the point where all ends of lines errors are reported. Reason For historical reasons, windows and Read more…
Last time, I deployed a React.js project on a server. But I found the router doesn’t work. I click the menu to other child pages. It always returns a 404 page. I did some search and found the reason. When Read more…