I recommend to always use for … of in ES6. It works on any iterable It supports all kinds of control flow in the loop body, like continue, break, return, yield and await. Also I personally find it more readable, but that comes down to preference. Some people think forEach is a more functional style, … Read more
The members of a class are not enumerable. To get them, you have to use Object.getOwnPropertyNames: var propertyNames = Object.getOwnPropertyNames(Object.getPrototypeOf(foo)); // or var propertyNames = Object.getOwnPropertyNames(Foo.prototype); Of course this won’t get inherited methods. There is no method that can give you all of them. You’d have to traverse the prototype chain and get the properties … Read more
This Babel plugin worked for me: https://github.com/loganfsmyth/babel-plugin-transform-decorators-legacy npm i –save-dev babel-plugin-transform-decorators-legacy .babelrc { “presets”: [“es2015”, “stage-0”, “react”], “plugins”: [ [“transform-decorators-legacy”], // … ] } or Webpack { test: /\.jsx?$/, loader: ‘babel’, query: { cacheDirectory: true, plugins: [‘transform-decorators-legacy’ ], presets: [‘es2015’, ‘stage-0’, ‘react’] } } React Native With react-native you must use the babel-preset-react-native-stage-0 plugin instead. … Read more
A good option is to use the constructor property of the object: // on reject / failure switch (error.constructor) { case NotAllowedError: return res.send(400); case DatabaseEntryNotFoundError: return res.send(404); default: log(‘Failed to do something async with an unspecified error: ‘, error); return res.send(500); } Notice that the constructor must match exactly with the one that object … Read more
Your syntax is valid. JSX is syntax sugar for React.createElement(type) so as long as type is a valid React type, it can be used in JSX “tags”. If Button is null, your import is not correct. Maybe Button is a default export from component-library. Try: import {default as StyledButton} from “component-library”; The other possibility is … Read more
const { bar, baz, …qux } = foo Now your object qux has all of the properties of foo except for bar and baz.
f => f is the identity function. It simply returns the argument that was passed in. This function is often used as a default values for transformation processes, since it doesn’t perform any transformation. Is f => f equivalent to () => {} an empty anonymous function? No. The empty function doesn’t return anything. The … Read more
Try wrapping the cases in blocks: switch(condition) { case ‘complex’: { const query_url = `something`; … // do something break; } default: { const query_url = `something`; … // do something else break; } }
A promise is just an object with properties in Javascript. There’s no magic to it. So failing to resolve or reject a promise just fails to ever change the state from “pending” to anything else. This doesn’t cause any fundamental problem in Javascript because a promise is just a regular Javascript object. The promise will … Read more
We do have dynamic imports proposal now with ECMA. This is in stage 2. This is also available as babel-preset. Following is way to do conditional rendering as per your case. if (foo === bar) { import(‘./Baz’) .then((Baz) => { console.log(Baz.Baz); }); } This basically returns a promise. Resolution of promise is expected to have … Read more