The each() method supplies two parameters to the callback-function. They are current index and the current item. Thus you could do the following: $(‘ul#mylist > li’).each((i, v) => { $(v).addClass(‘some-class-name’); }); Where the “v” variable is the current “li” element
The React FAQs provide an explanation to it Are Hooks slow because of creating functions in render? No. In modern browsers, the raw performance of closures compared to classes doesn’t differ significantly except in extreme scenarios. In addition, consider that the design of Hooks is more efficient in a couple ways: Hooks avoid a lot … Read more
Is it possible to export Arrow functions in ES6/7? Yes. export doesn’t care about the value you want to export. The export statement below gives a syntax error … why? You cannot have a default export and give it a name (“default” is already the name of the export). Either do export default () => … Read more
The fat arrow binds at 3 occasions when declaring a method when declaring a function within a method when declaring a function in global context 1. When declaring a method When the Coffeescript compiler encouters the following syntactical pattern within a class declaration class A somemethod: (paramlist) => This will yield the following code within … Read more
If you don’t use a block ({}) as body of an arrow function, the body must be an expression: ArrowFunction: ArrowParameters[no LineTerminator here] => ConciseBody ConciseBody: [lookahead ≠ { ] AssignmentExpression { FunctionBody } But throw is a statement, not an expression. In theory () => throw x; is equivalent to () => { return … Read more
How can I differentiate between these things in ES6? arrow functions are functions that cannot be used as constructors, and don’t have a .prototype property. However, methods don’t either. They inherit from Function.prototype. classes are functions that can’t be called without new, and that have a .prototype object which is normally not empty. If the … Read more
No, that’s not the rule I would use. The major use-case I’ve found for the fat-arrow in defining methods is when you want to use a method as a callback and that method references instance fields: class A constructor: (@msg) -> thin: -> alert @msg fat: => alert @msg x = new A(“yo”) x.thin() #alerts … Read more
As already stated in this comment and this answer, this does not have a different meaning between JavaScript and TypeScript. That being said, your problem here is way more prosaic: you’re trying to use this in an arrow function to get the current DOM element, and that will simply not work. So, in a nutshell, … Read more
The short answer is because arrow function is recreated every time, which will hurt the performance. This is a common misconception. The arrow function is recreated every time either way (although with useCallback subsequent ones may be thrown away immediately). What useCallback does is make it possible for the child component you use the callback … Read more
This is normal. Unlike a function expression, which is a PrimaryExpression like other literals and identifiers, and arrow function specifically is an AssignmentExpression and can only appear inside grouping, comma, assignment, conditional (ternary) and yield expressions. Any other operator than those would lead to ambiguities. For example, if you expect y || ()=>z to work, … Read more