This is a fact of the new class syntax. Your subclass needs to call super() in order for the class to be properly initialized, e.g. super(arg1, arg2, argN); with whatever arguments the parent constructor needs. It is required that, if execution reaches the end of a constructor function, the value of this needs to have … Read more
this error should only arise if the array or object being destructured or its children is undefined or null. Exactly. In your case, the object being destructured is either undefined or null. For example, function test(err, {a, b, c}) { console.log(err, a, b, c); } test(1, {a: 2, b: 3, c: 4}); // 1 2 … Read more
Bergi’s answer is excellent, and has been very helpful to me. This answer is complementary to his. In order to visualize the relationship between the Promise() constructor and the then() method, I created this diagram. I hope it helps somebody… maybe even me, a few months months from now. The main idea here is that … Read more
what would be an appropriate way to write foo to achieve this? If you mean to default only when there is no parameter passed to the function call, then you need to check the arguments length, or to spread the arguments if you want to keep an arrow function. const foo = (…args) => { … Read more
The main purpose of Symbol.toPrimitive is to change the order in which toString and valueOf are called in different coercion scenarios. An example of this is the Date native object, where it will convert the value to a string instead of a number by default: console.log(1 + new Date()); // “1Mon Aug 15 2016 13:25:31 … Read more
Observables push changes, and hence the observable, not the function reacting to it, is in control. Generators on the other hand require you to pull values out of them. So the function that will react to the new value determines when it is ready for a new value. I had trouble with backpressure using observables, … Read more
That is not actually a babel issue, you are just trying to run CommonJS code (transpiled from ES6 export) in the browser without preparation. CommonJS doesn’t run on the browser, you need to use a tool to package it for the browser, such as Webpack or Browserify. Just by coincidence this week I created a … Read more
The …(spread operator) works by returning each value from index 0 to index length-1: As example: […’18’] // returns [‘1’, ‘8’] which would be the same as: [’18′[0], ’18′[1]] Now, to get an array from 1 to 18, you can do this: […Array(19).keys()].slice(1) Or this with map: […Array(18)].map(_=>i++,i=1) Hope it helps.
You’d want to use Object.keys(settings).forEach(key => { Object.keys(env[key]).forEach(subkey => { or potentially Object.entries or Object.values depending on if you actually want the keys.
As with any other object you want to stringify in JS, you can use JSON.stringify: JSON.stringify(yourObject); class MyClass { constructor() { this.foo = 3 } } var myClass = new MyClass() console.log(JSON.stringify(myClass)); Also worth noting is that you can customize how stringify serializes your object by giving it a toJSON method. The value used to … Read more