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Overview of JavaScript ES6 features

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Re: Overview of JavaScript ES6 features

#31

Post by ubertaco »

mattmanser wrote: post #6

destructing is very useful and encourage good coding styles Is it? Personally I'd say that was bad code. What so wrong with using the original objects? Putting aside the need to variable swap once a year or so, all the other examples look really confusing to me and unclear what they're doing. The `Deep Matching` especially.

It's really nice for when you have to do operations where you want a "tuple" in Javascript.

Consider the case of finding all companies along with their hires from the last week, but only if the company has a hire from the last week:

    companies.map(c => [c, employeeStorage.getEmployees(c)])
             .map(([company, employees]) => [company, employees.filter(e => e.hireDate > aWeekAgo)])
             .filter(([company, employees]) => employees.length > 0)

Re: Overview of JavaScript ES6 features

#32

Post by gbog »

z3t4 wrote: post #19

var's function scope is a feature! You don't have to place variable declarations in the header! (they are hoisted) Placing the var declarations where they are used makes the code easier to understand. The point of constructor functions is not having to write new . So classes does nothing besides syntactic sugars over the prototype system, witch actually makes it more complicated and the code harder to maintain. Async…

> You should always name your closures

Yes. Why? Because you should have readable tracebacks. Why? Because you should receive all meaningful errors reports from the devices.

Re: Overview of JavaScript ES6 features

#33

Post by treve »

Tankenstein wrote: post #12
my123 wrote: post #7

On the web browser side, I don't recommend using ES6 yet, without any kind of fallback. Internet Explorer 11 is still used, as are devices on older iOS versions. (without counting people using the default browser on pre-Lollipop Android)

For anyone who wants to use ES6 in production, https://babeljs.io/ is amazing.

It's both amazing, and 600MB worth of dependencies. We use it for server-side code. It's high quality, and we only have a few issues with it, but I can't wait to be able to ditch is (pretty much when async/await lands in a stable node).

Re: Overview of JavaScript ES6 features

#34

Post by [deleted] »

Tankenstein wrote: post #12
my123 wrote: post #7

On the web browser side, I don't recommend using ES6 yet, without any kind of fallback. Internet Explorer 11 is still used, as are devices on older iOS versions. (without counting people using the default browser on pre-Lollipop Android)

For anyone who wants to use ES6 in production, https://babeljs.io/ is amazing.

[deleted]

Re: Overview of JavaScript ES6 features

#35

Post by epmatsw »

z3t4 wrote: post #19

var's function scope is a feature! You don't have to place variable declarations in the header! (they are hoisted) Placing the var declarations where they are used makes the code easier to understand. The point of constructor functions is not having to write new . So classes does nothing besides syntactic sugars over the prototype system, witch actually makes it more complicated and the code harder to maintain. Async…

Promises and callbacks have fundamentally different behavior. Promises are much more reliable (only executed a single time, always executed asynchronously vs possibly synchronously, etc.) and also have slightly different execution behavior in the event loop. People emphasize the syntax differences, but that's not the most useful thing about Promises imo. You Don't Know JS's async book has an excellent in-depth writeup on it.

Re: Overview of JavaScript ES6 features

#36

Post by TheAceOfHearts »

my123 wrote: post #7

On the web browser side, I don't recommend using ES6 yet, without any kind of fallback. Internet Explorer 11 is still used, as are devices on older iOS versions. (without counting people using the default browser on pre-Lollipop Android)

You should be using babel to serve all your target browsers. But you can still use ES2015 during development; it's an absolute joy.

Re: Overview of JavaScript ES6 features

#37

Post by megous »

jaquers wrote: post #11
my123 wrote: post #7

On the web browser side, I don't recommend using ES6 yet, without any kind of fallback. Internet Explorer 11 is still used, as are devices on older iOS versions. (without counting people using the default browser on pre-Lollipop Android)

Indeed. Are there any 'good' strategies for this (loading ES6 for supported browsers)? I imagine you'd have to do UA sniffing on the server side, and I suppose it's kind of a moot point if you're using React/JSX.

Just try to eval a sample of ES6 syntax you use, and if it throws error, load ES5 code. You'd need to feature check all the features that you use, to cover the browser versions with incomplete ES6 support.

Re: Overview of JavaScript ES6 features

#39

Post by ggregoire »

I'm surprised by the state of const/let nowadays.

The well-known good practice: use const by default; use let when it's needed. At the release of ES6, it was the way to go. But everyday I notice libraries—and some really famous— that use let everywhere in their docs, or some really influent developers from Google or Facebook who share samples of code on Twitter using let when it's not needed [1]. I don't know why. Seems like most people now think that const is for declaring constants (in the traditional meaning, like const API_URL) when it's just the normal way to declare variables that don't need to be reassigned (so basically most variables).

Dan Abramov said: "some people say const is ugly" [2]. Well, if it's a matter of appearance...

[1] https://twitter.com/addyosmani/status/789126892402204673

[2] https://twitter.com/dan_abramov/status/783708858803978240

Re: Overview of JavaScript ES6 features

#40

Post by ChemicalWarfare »

z3t4 wrote: post #19

var's function scope is a feature! You don't have to place variable declarations in the header! (they are hoisted) Placing the var declarations where they are used makes the code easier to understand. The point of constructor functions is not having to write new . So classes does nothing besides syntactic sugars over the prototype system, witch actually makes it more complicated and the code harder to maintain. Async…

>>> You don't have to place variable declarations in the header! (they are hoisted)

probably splitting hairs here but imo "hoisting" as in using variables before they are declared is generally a bad practice especially considering that init assignments are not "hoisted".

>>>Arrow functions are very nice for one liners, but will ruin your code if you use them everywhere instead of named functions.

Based on arrow functions' relationship with "this" pretty sure the intent is to primarily use arrow functions instead of anonymous functions especially when passing them around as params. Even with one-liners you have to be wary of what "this" is when dealing with an arrow function inside of an object for example.

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