According to dis, they all get compiled to the same bytecode: >>> def f1(line): … a,b,c = line.split() … >>> def f2(line): … (a,b,c) = line.split() … >>> def f3(line): … [a,b,c] = line.split() … >>> import dis >>> dis.dis(f1) 2 0 LOAD_FAST 0 (line) 3 LOAD_ATTR 0 (split) 6 CALL_FUNCTION 0 9 UNPACK_SEQUENCE 3 … Read more
It seems like you can’t differentiate variable’s declaration in a one line. However, you could split it into two lines and use a different variable declaration, depends on which variable you want to get. const { a } = foo; let { b } = foo;
I caused this error a few times because whenever I write a useState hook, which I would do often, I’m used to using an array to destructure like so: const [ state, setState ] = useState(); But my custom hooks usually return an object with properties: const { data, isLoading } = useMyCustomFetchApiHook(); Sometime I … Read more
You can only do it slightly more elegantly by omitting the var keyword for each variable and separating the expressions by commas: var array = str.split(‘-‘), a = array[0], b = array[1], c = array[2]; ES6 standardises destructuring assignment, which allows you to do what Firefox has supported for quite a while now: var [a, … Read more
Just like you cannot declare a variable with a hyphen, you can’t destructure directly to one. You will need to rename your variable to something else in order to access it on the current scope. You can use the following destructuring syntax to do that: const x = { “accept-ranges”:”bytes”, “cache-control”:”public, max-age=0″, “content-length”:”1174″, “content-type”:”application/json”, date:”Mon, … Read more
I talked to several people on Discord #reactiflux channel and actually got the answer I was looking for. There are basically three use-case with React components, and in some of them, destructuring params will impact performances so it is important to understand what’s going on under the hood. Stateless functional component const MyComponent = ({ … Read more
In C++17 this is called structured bindings, which allows for the following: struct animal { std::string species; int weight; std::string sound; }; int main() { auto pluto = animal { “dog”, 23, “woof” }; auto [ species, weight, sound ] = pluto; std::cout << “species=” << species << ” weight=” << weight << ” sound=” … Read more
Update for node v6 and newer: Node v6 supports destructuring assignment without anything special needed: var [a, b] = [1, 2]; For older versions of node: You can get the list of supported harmony features by typing: node –v8-options | grep harmony node 5.x will give you: –es_staging (enable all completed harmony features) –harmony (enable … Read more
Can I avoid declaring a useless variable when array destructuring when I am only interested in array values beyond index 0? Yes, if you leave the first index of your assignment empty, nothing will be assigned. This behavior is explained here. // The first value in array will not be assigned const [, b, …rest] … Read more
import {Link} from ‘react-router’; imports a named export from react-router, i.e. something like export const Link = 42; import Router from ‘react-router’; const {Link} = Router; pulls out the property Link from the default export, assuming it is an object, e.g. export default { Link: 42 }; (the default export is actually nothing but a … Read more