As G.aziz said, React.memo functions similarly to pure component. However, you can also adjust its behavior by passing it a function which defines what counts as equal. Basically, this function is shouldComponentUpdate, except you return true if you want it to not render. const areEqual = (prevProps, nextProps) => true; const MyComponent = React.memo(props => … Read more
Writing a recursive function without naming it is a problem that is as old as computer science itself (even older, actually, since λ-calculus predates computer science), since in λ-calculus all functions are anonymous, and yet you still need recursion. The solution is to use a fixpoint combinator, usually the Y combinator. This looks something like … Read more
Hi and welcome to React! I think part of what you’re having trouble with here is not really React-specific, but instead related to the new ES2015 module syntax. When creating React class components, for most intents and purposes you can think of React.createClass as functionally equivalent to class MyComponent extends React.Component. One is just using … Read more
This is a general JS issue, but the core of it is that this.elm.addEventListener(‘click’, this.sayHello); is no different than var fn = this.sayHello; this.elm.addEventListener(‘click’, fn); You are passing a function as the event handler, but have not ensured that when fn is called that this will be set to your desired value. The easiest way … Read more
When you are destructuring an Object, you need to use the same variable names as the keys in the object. Only then you will get one to one correspondence and the values will be destructured properly. and you need to wrap the entire assignment in parenthesis if you are not using declaration statement, otherwise the … Read more
You’ll need to move your logic into a function or use the ternary operator: `${result[‘color 5’] ? ‘color 5 exists!’ : ‘color 5 does not exist!’}` Additional example based on comment: `${result[‘color 5’] ? `<div class=”color” style=background-color:#${result[‘color 5’]}><h6>${result[‘color 5’]}</h6></div>` : ”}`
I would say its because while Math.pow(2, 53) is the largest directly representable integer, its unsafe in that its also the first value who’s representation is also an approximation of another value: 9007199254740992 == 9007199254740993 // true In contrast to Math.pow(2, 53) – 1: 9007199254740991 == 9007199254740993 // false
Yes, it is perfectly fine to add elements and remove elements to a set while iterating it. This use case was considered and is supported in JavaScript 2015 (ES6). It will leave it in a consistent state. Note this also applies to itearting with forEach. Intuitively: The set iteration algorithm basically looks something like this: … Read more
Late to the party, but since I had a similar problem (Use global nest module in decorator) and stumbled upon this question. import { Inject } from ‘@nestjs/common’; export function yourDecorator() { const injectYourService = Inject(YourServiceClass); return (target: any, propertyKey: string, propertyDescriptor: PropertyDescriptor) => { // this is equivalent to have a constructor like constructor(yourservice: … Read more
I would say that this is a bit opinionated choice really. There are at least several reasons why I (personally) see arrow function use for a purely functional component as pretty bad practice. Here are those: Syntax abuse. When we define function component we don’t need to pre-bind its context to a specific scope. The … Read more