Use object destructuring to get the properties, and generate a new object using shorthand property names: const dummyArray = [{ “att20”: “att20”, “att30”: “att30”, “att70”: “att70”, “att80”: “att80”}, { “att20”: “att20”, “att30”: “att30”, “att70”: “att70”, “att80”: “att80”}]; const result = dummyArray.map(({ att20, att30, att70, att80 }) => ({ att20, att30, att70, att80 })); console.log(result);
Note: I’ve posted this as a community wiki, we can all add to the list, clarify, etc. Please no opinions. Keep it objective. Or is this just a matter of taste/style guide etc? There will be a strong influence of style, yes, but there are some objective observations we can make in terms of the … Read more
Is it a good practice to call a child method from a parent class? Yes, it’s a totally normal practise. The parent class just calls some method of the instance, and if the child class has overridden the method then the child method is called. However, you usually wouldn’t do such a “has my instance … Read more
Yes, this is intentional (a part of the spec). If an object has an own property (.property in your example), this property will be used and not an inherited one. If that property is existent, but is an accessor property without a getter, then undefined will be returned. Notice that this behaviour has not changed … Read more
Your update function would look like this updateItem(id, itemAttributes) { var index = this.state.items.findIndex(x=> x.id === id); if (index === -1) // handle error else this.setState({ items: [ …this.state.items.slice(0,index), Object.assign({}, this.state.items[index], itemAttributes), …this.state.items.slice(index+1) ] }); } And you use it like this this.updateItem(2, {someattr: ‘a new value’}); Gross right? You’re going to have a big … Read more
As noted in the comments, and summarized by @ftor from #687, object spread is equivalent1 to Object.assign() (issues #687, #45), whereas spread in array literal context is iterable spread. Quoting Ecma-262 6.0, Object.assign() is defined as: 19.1.2.1 Object.assign ( target, …sources ) The assign function is used to copy the values of all of the … Read more
A year and some later, here is the best information I’ve found on the subject. There are 4 types of exports. Here are usage examples of each, along with some imports that use them: Export Syntax // default exports export default 42; export default {}; export default []; export default (1 + 2); export default … Read more
What is an applicable example of using Maps over objects? I think you’ve given one good example already: You at least need to use Maps when you are using objects (including Function objects) as keys. in particular, “when would keys be unknown until runtime?” Whenever they are not known at compile time. In short, you … Read more
No, there are no nested class scopes in ES6, and there is no such thing as private members in the class syntax anyway if you mean that. Of course you can put a second class as a static property on another class, like this: class A { … } A.B = class { … }; … Read more
super() will call the constructor of its parent class. This is required when you need to access some variables from the parent class. In React, when you call super with props, React will make props available across the component through this.props. See example 2 below without super() class A { constructor() { this.a=”hello” } } … Read more