There seems something inherently wrong with having to define a Promise’s callback as asynchronous: This is apparently an antipattern and there are coding problems which can arise from it. I understand that it becomes easier to fail to catch errors here, even when placing await statements inside try/catc…
Tag: ecmascript-6
Unable to display Date in JSX in ReactJS
Following is my code which is working fine if I initialize test with a string, though if I changed it to new Date() its throwing error. Let me know what I am doing wrong as I just started with React. Code – Error – Objects are not valid as a React child (found: Fri Jul 21 2017 02:11:18 GMT+0530 (I…
How to properly use Object.setPrototypeOf()
So I’ve been getting up to speed on some of the newer features of JavaScript and have been reading about Object.setPrototypeOf(). I ran across this bit of code from MDN which deals with inheriting from regular objects. But I’m confused at how they use Object.setPrototypeOf() here. I expected them …
Programmatically cause onBlur to trigger in react
I use onBlur to close a dropdown, but I also want to handle a click handler of an li which is render within, setState won’t work here, the behavior is broken when user try to open the dropdown again, try it here: http://jsfiddle.net/ur1rbcrz My code: Answer Your code is not working because, even though …
ReactJS “Unhandled Rejection (TypeError): this.state.features.map is not a function”
I’m learning React and now I’m trying to do a get request and list with map but when I run this code they come up with this error “Unhandled Rejection (TypeError): this.state.features.map is not a function”. I have already searched this but I do not understand what is going on. Answer …
Enums in Javascript with ES6
I’m rebuilding an old Java project in Javascript, and realized that there’s no good way to do enums in JS. The best I can come up with is: The const keeps Colors from being reassigned, and freezing it prevents mutating the keys and values. I’m using Symbols so that Colors.RED is not equal to…
ES6 – is there an elegant way to import all named exports but not the default export?
I am looking for an elegant way to import all named exports without having to import the default as well. In one file I am exporting many named constants plus a default: In another file I would like to have an elegant way to import all named exports only, without having to import the default: I do not want to…
Jest equivalent to RSpec lazy evaluated variables (let)?
In rspec you can do something like this: This allows you to define a method call or instantiation of a large object as a sum of its smaller parts. You can then override those individual small parts inside different contexts. The idea being that you create a happy path before each test, and then specify deviat…
Update one of the objects in array, in an immutable way
In React’s this.state I have a property called formErrors containing the following dynamic array of objects. Let’s say I would need to update state’s object having the fieldName cityId to the valid value of true. What’s the easiest or most common way to solve this? I’m OK to use …
Why would you try-catch around a promise? Does that catch the promise’s error?
I stumbled upon some code that looked off to me: If some somePromise() fails, would this not get caught, and the app would crash? Does this try-catch even do anything? Should be this, correct?: Answer TL;DR – If a function that returns a promise throws an exception before returning the promise then that…