Chrome, FF, and node seem to be wrong here, Babel is correct: Arrow functions do not have an own arguments binding in their scope; no arguments object is created when calling them. looking for official docs here Arrow function expressions evaluate to functions that have their [[ThisMode]] set to lexical, and when such are called … Read more
Arrow functions provide a lexical this. It uses the this that is available at the time the function is evaluated. It is logically equivalent to (the following isn’t valid code since you can’t have a variable named this): (function(this){ // code that uses “this” })(this) In your 1st example the arrow function is within the … Read more
There are no (significant) differences. Well, okay, that’s a little premature. There are three tiny differences unique to arrow functions. Arrow functions cannot be used with new. This means, of course, that they do not have a prototype property and cannot be used to create an object with the classically-inspired syntax. new (() => {}) … Read more
First of all, let’s start with examples of each technique! But the difference is more related to JavaScript language itself. Binding: import React from ‘react’; class MyComponent extends React.Component { constructor(props) { super(props) this.clickHandler = this.clickHandler.bind(this); } clickHandler() { console.log( this ) } render() { return <button onClick={this.clickHandler}>Click Me</button> } } Arrow-function: import React from … Read more
I had the error expression expected reported by Webstorm when editing a Node.js program. In this case the solution is to set the language version to a version that supports this feature.
I understand that arrow functions make things more efficient by not recreating the functions each time they are referred to This is not true. Arrow functions handles the this context in a lexical way, where “normal” function do it dynamically. I wrote about the this key word in depth if you need more info about … Read more
Arrow functions capture the this value of the enclosing context function Person(){ this.age = 0; setInterval(() => { this.age++; // |this| properly refers to the person object }, 1000); } var p = new Person(); So, to directly answer your question, this inside your arrow function would have the same value as it did right … Read more
I guess it was added inbetween then and now, because you can do it now using an interface or type (doesnt matter, same syntax except the keyword). Also works as export of course. The function has to be named though (i think all overloaded functions have to), so you’ll have to declare it first if … Read more
Put parens around the object initializer: data.map((d) => ({id: d.id, selected: bool}) ); Parentheses have no effect on the value of the expression inside them, but they do have the syntactic effect of eliminating the ambiguity of the first token of the contained expression. Without the parentheses, the JavaScript parser has to decide whether the … Read more
The parenthesis are returning a single value, the curly braces are executing multiple lines of code. Your example looks confusing because it’s using JSX which looks like multiple “lines” but really just gets compiled to a single “element.” Here are some more examples that all do the same thing: const a = (who) => “hello … Read more