Using the ES2015 Spread operator: […Array(n)].map() const res = […Array(10)].map((_, i) => { return i * 10; }); // as a one liner const res = […Array(10)].map((_, i) => i * 10); Or if you don’t need the result: […Array(10)].forEach((_, i) => { console.log(i); }); // as a one liner […Array(10)].forEach((_, i) => console.log(i)); Or … Read more
No. The bind operator (spec proposal) comes in two flavours: Method extraction ::obj.method ≡ obj.method.bind(obj) “virtual method” calls obj::function ≡ function.bind(obj) obj::function(…) ≡ function.call(obj, …) Neither of them feature partial application. For what you want, you should use an arrow function: (…args) => this.handleStuff(‘stuff’, …args) ≡ this.handleStuff.bind(this, ‘stuff’)
If you use Babel you can use the following syntax to copy property b from x into variable b and then copy rest of properties into variable y: let x = {a: 1, b: 2, c: 3, z:26}; let {b, …y} = x; and it will be transpiled into: “use strict”; function _objectWithoutProperties(obj, keys) { … Read more
The original motivation for introducing symbols to Javascript was to enable private properties. Unfortunately, they ended up being severely downgraded. They are no longer private, since you can find them via reflection, for example, using Object.getOwnPropertySymbols or proxies. They are now known as unique symbols and their only intended use is to avoid name clashes … Read more
Update 3/2022 There is currently a proposal to add Records and Tuples (basically immutable Objects and Arrays) to Javascript. In that proposal, it offers direct comparison of Records and Tuples using === or !== where it compares values, not just object references AND relevant to this answer both Set and Map objects would use the … Read more
A while ago our team migrated all its code (a mid-sized AngularJS app) to JavaScript compiled using Traceur Babel. I’m now using the following rule of thumb for functions in ES6 and beyond: Use function in the global scope and for Object.prototype properties. Use class for object constructors. Use => everywhere else. Why use arrow … Read more
Here’s something slimmer, although it doesn’t avoid repeating the list of fields. It uses “parameter destructuring” to avoid the need for the v parameter. ({id, title}) => ({id, title}) (See a runnable example in this other answer). @EthanBrown’s solution is more general. Here is a more idiomatic version of it which uses Object.assign, and computed … Read more
Arrow functions are not designed to be used in every situation merely as a shorter version of old-fashioned functions. They are not intended to replace function syntax using the function keyword. The most common use case for arrow functions is as short “lambdas” which do not redefine this, often used when passing a function as … Read more