Updated below for ES6 March 2013 and ES5 This MDN document describes extending classes well: https://developer.mozilla.org/en-US/docs/JavaScript/Introduction_to_Object-Oriented_JavaScript In particular, here is now they handle it: // define the Person Class function Person() {} Person.prototype.walk = function(){ alert (‘I am walking!’); }; Person.prototype.sayHello = function(){ alert (‘hello’); }; // define the Student class function Student() { // … Read more
Add the babel-cli and babel-preset-es2015 (aka ES6) dependencies to your app’s package.json file and define a start script: { “dependencies”: { “babel-cli”: “^6.0.0”, “babel-preset-es2015”: “^6.0.0” }, “scripts”: { “start”: “babel-node –presets es2015 app.js” } } Then you can simply execute the following command to run your app: npm start If you ever decide to stop … Read more
When using spread, you are expanding a single variable into more: var abc = [‘a’, ‘b’, ‘c’]; var def = [‘d’, ‘e’, ‘f’]; var alpha = [ …abc, …def ]; console.log(alpha)// alpha == [‘a’, ‘b’, ‘c’, ‘d’, ‘e’, ‘f’]; When using rest arguments, you are collapsing all remaining arguments of a function into one array: … Read more
Spread element (it’s not an operator) works only with objects that are iterable (i.e. implement the @@iterator method). Array.from() works also on array-like objects (i.e. objects that have the length property and indexed elements) which are not iterable. See this example: const arrayLikeObject = { 0: ‘a’, 1: ‘b’, length: 2 }; // This logs … Read more
The correct way is to continue using the old import syntax. The new import syntax is for ES modules only, the old import syntax is for pre-ES6 modules. The two are distinct, intentionally so. import * as foo from ‘foo’ imports all the properties of the module ‘foo’, it does not import the default value … Read more
Feature detection I suggest you to use feature detection instead of detecting the browser’s engine with heuristic methods. To do this you can simply wrap some code inside a try {..} catch (e) {…} statement, or use some if (…) statements. For example: function check() { if (typeof SpecialObject == “undefined”) return false; try { … Read more
In my current project I also needed a way of defining if something was already a Proxy, mainly because I didn’t want to start a proxy on a proxy. For this I simply added a getter to my handler, which would return true if the requested variable was “__Proxy”: function _observe(obj) { if (obj.__isProxy === … Read more
If we want to use .filter() iterator for a map, we can apply a simple trick, because there is no .filter operator for ES6 Maps. The approach from Dr. Axel Rauschmayer is: Convert the map into an array of [key, value] pairs. Map or filter the array. Convert the result back to a map. Example: … Read more
Settings/Preferences | Editor | Inspections JavaScript | Code style issues | Unterminated statement — disable this inspection You can also reach the same inspection by: Placing caret on problematic place in your Editor and bringing Quick Fix menu (Alt + Enter or by clicking on light bulb icon) Choosing right option in appeared menu (if … Read more
Put parens around the object initializer: data.map((d) => ({id: d.id, selected: bool}) ); Parentheses have no effect on the value of the expression inside them, but they do have the syntactic effect of eliminating the ambiguity of the first token of the contained expression. Without the parentheses, the JavaScript parser has to decide whether the … Read more