Cons/Dislikes

• No conventions.

• Not standardized.

• No consistency in online resources.

  • Lots of outdated online resources.

  • The fact that AirBNB has 20 pages on how to write JavaScript is insane.

• No first class Enums

• No types. Can be handled by Flow or TypeScript​

• Callback hell (work around with Promises, async and await, but its not supported everywhere)

• Inconsisent: Array.length vs Set.size

  • Like wtf?

• All the problems of a loosely typed language.

  • Hard to scale as a language, due to no types.

  • Hard to refactor.

• Inconsistencies in coding style amongst the community

• JS Modules are confusing

• Requires high code coverage due to inconsistencies.

• Changing babel flags can make your code run differently

  • Requires high code coverage to ensure it does as expected.

• You need tools like lodash for basic stuff (bucketing items in in an array, groupBy)

• Requires a lot of tooling to maintain JavaScript

• Was design for client side browsing, not server side

• It has both null and undefined

• No native sprintf

• Browser support is inconsistent.

  • I ran into a problem with fetch() not being supported. https://github.com/github/fetch#browser-support​

• Requires a lot of static analysis tools.

  • jshint http://jshint.com/about/

  • flow

• See Node.js's creator Ryan Dahl's "10 Things I Regret About Node.js"

What does this return?

"some string".match(/some regex/)

It's an Array with properties of index and input.

Things which increase the JavaScript environments complexity:

• Requiring the use of new features via Babel

• Requiring WebPack to bundle for frontend

• Module systems

• Inconsistent environments

  • Browser development, so many browser versions

  • Node, webpack vs everything else

Array.flat

Array.flat only works in Node.js 11+

​https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/flat​

Array.values() is different from Object.values()

Object.values(object) returns an array of values

array.values() returns an iterator

​https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/values​

​https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/values​

No easy way to test that two Sets are equal

new Set(['a', 'b']) == new Set(['b', 'a']); // false

​https://stackoverflow.com/questions/31128855/comparing-ecma6-sets-for-equality​