This isn’t necessarily exhaustive. Spread syntax options = {…optionsDefault, …options}; Advantages: If authoring code for execution in environments without native support, you may be able to just compile this syntax (as opposed to using a polyfill). (With Babel, for example.) Less verbose. Disadvantages: When this answer was originally written, this was a proposal, not standardized. … Read more
In order to setState for a nested object you can follow the below approach as I think setState doesn’t handle nested updates. var someProperty = {…this.state.someProperty} someProperty.flag = true; this.setState({someProperty}) The idea is to create a dummy object perform operations on it and then replace the component’s state with the updated object Now, the spread … Read more
I use ES6 template literals. For example: const error = this.state.valid ? ” : ‘error’ const classes = `form-control round-lg ${error}` And then just render it: <input className={classes} /> One-liner version: <input className={`form-control round-lg ${this.state.valid ? ” : ‘error’}`} />
There is only one reason when one needs to pass props to super(): When you want to access this.props in constructor. Passing: class MyComponent extends React.Component { constructor(props) { super(props) console.log(this.props) // -> { icon: ‘home’, … } } } Not passing: class MyComponent extends React.Component { constructor(props) { super() console.log(this.props) // -> undefined // … Read more
That is a curried function First, examine this function with two parameters … const add = (x, y) => x + y add(2, 3) //=> 5 Here it is again in curried form … const add = x => y => x + y Here is the same1 code without arrow functions … const add … Read more
defaultMember already is an alias – it doesn’t need to be the name of the exported function/thing. Just do import alias from ‘my-module’; Alternatively you can do import {default as alias} from ‘my-module’; but that’s rather esoteric.
tl;dr: No! Arrow functions and function declarations / expressions are not equivalent and cannot be replaced blindly. If the function you want to replace does not use this, arguments and is not called with new, then yes. As so often: it depends. Arrow functions have different behavior than function declarations / expressions, so let’s have … Read more
You can await on Promise.all(): await Promise.all([someCall(), anotherCall()]); To store the results: let [someResult, anotherResult] = await Promise.all([someCall(), anotherCall()]); Note that Promise.all fails fast, which means that as soon as one of the promises supplied to it rejects, then the entire thing rejects. const happy = (v, ms) => new Promise((resolve) => setTimeout(() => resolve(v), … Read more
I got this error because I forgot the type=”module” inside the script tag: <script type=”module” src=”milsymbol-2.0.0/src/milsymbol.js”></script>
You must wrap the returning object literal into parentheses. Otherwise curly braces will be considered to denote the function’s body. The following works: p => ({ foo: ‘bar’ }); You don’t need to wrap any other expression into parentheses: p => 10; p => ‘foo’; p => true; p => [1,2,3]; p => null; p … Read more