uhhh edge still hasn't destructuring
Overview of JavaScript ES6 features
211–220 of 250 posts
Re: Overview of JavaScript ES6 features
#212I'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. Se…
it's sad the longest of [var, let, const] is the most useful one. They should have made let behave like const
Re: Overview of JavaScript ES6 features
#213Earlier quoted context omitted.
From the article-- let x = 'outer'; function test(inner) { if (inner) { let x = 'inner'; return x; } return x; // gets result from line 1 as expected } test(false); // outer test(true); // inner This makes it seem like let creates global variables. Why would you want to return a variable from outside the function? Doesn't that create massive overhead in terms of keeping track where variables are initially set? Easy t…
If you were to then reference 'x' from another block of code, say in another element in the case of web development, 'x' would not be a defined variable, whereas with 'var', it would be. This is mostly just a case of 'let' restricting a variable to the block it is in, and the child blocks. In your example, `let x = 'outer';` is sort of acting like a global variable, but the importance is that if another script were t…
Ehw. Yeah, I sort of assumed that you had a top level function / IIFE (in a .js file, FWIW) in which the var's were nested.
Somebody writing stuff, into the global namespace, directly in tags, has bigger problems :-)
Re: Overview of JavaScript ES6 features
#214Earlier quoted context omitted.
I believe that you're getting that number, but there might be something wrong with your install. I just installed all of those packages and ended up at 6MB.
I don't think it's such a stretch. From facebook's yarn announcement[1]: > or example, updating a minor version of babel generated an 800,000-line commit that was difficult to land and triggered lint rules for invalid utf8 byte sequences, windows line endings, non png-crushed images, and more. Merging changes to node_modules would often take engineers an entire day. I just did a fresh install in a new directory and e…
mkdir babel-size-check
cd babel-size-check
babel-size-check yarn init -y
yarn init v0.16.0
warning The yes flag has been set. This will automatically answer yes to all questions which may have security implications.
success Saved package.json
Done in 0.05s.
babel-size-check yarn add babel babel-core babel-eslint babel-plugin-array-includes babel-plugin-transform-runtime babel-preset-node5 babel-register babel-runtime
yarn add v0.16.0
info No lockfile found.
[1/4] Resolving packages...
warning babel@6.5.2: Babel's CLI commands have been moved from the babel package to the babel-cli package
[2/4] Fetching packages...
[3/4] Linking dependencies...
[4/4] Building fresh packages...
success Saved lockfile.
success Saved 80 new dependencies.
...
Done in 1.94s.
babel-size-check du -ch -d1
17M ./node_modules
17M .
17M totalRe: Overview of JavaScript ES6 features
#215I'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. Se…
How do you feel about `const` for variables that are not reassigned but are still mutated? const array = [1, 2, 3]; array.push(100); // unexpected? I prefer to use let for bindings to objects that get mutated, even if the variable is not re-bound.
As far as I know, the "correct" approach is to act as if every object is deeply frozen (perhaps actively testing using Object.freeze... IMO https://github.com/ecomfe/babel-plugin-freeze-const has the right idea but is nothing more than an idea), and transform things into new objects functionally, using .map and friends.
The problem is that, while a lot of things can be expressed elegantly this way, sometimes the most maintainable thing, or the most efficient thing, is to have some side effects in a deep loop in a certain algorithm, and it's very difficult to do this with purely functional JS.
The real solution is to allow your const bindings to be mutated when you need to, and comment explicitly to make things perfectly clear!
Re: Overview of JavaScript ES6 features
#216Earlier quoted context omitted.
> C++ constness is significantly more far-reaching and therefore more work to get right. I'm not familiar with C++, can you explain more?
A const variable means that variable won't change. So `const int i = 6` means i will never change. But often you'll use pointers or references, these are C++'s way for a variable to point to data elsewhere. You can also make the pointers or references themselves const. Finally, you can make functions const too, which lets you turn C++ into half a haskell. First pointers and references. For simplicitly I'm going to ig…
If you didn't want a to be mutated, you'd make it const in the beginning :)
Rust makes it much harder to make these kinds of erros by making variable ownership, reference lifetime, and const-by-default core to the language design. https://doc.rust-lang.org/book/ownership.html ... You do end up spending a lot of time "fighting the compiler," even compared to template-heavy C++ codebases, but the systems you create are free from an entire class of errors.
Re: Overview of JavaScript ES6 features
#217Earlier quoted context omitted.
> C++ constness is significantly more far-reaching and therefore more work to get right. I'm not familiar with C++, can you explain more?
A const variable means that variable won't change. So `const int i = 6` means i will never change. But often you'll use pointers or references, these are C++'s way for a variable to point to data elsewhere. You can also make the pointers or references themselves const. Finally, you can make functions const too, which lets you turn C++ into half a haskell. First pointers and references. For simplicitly I'm going to ig…
I'm not sure if you meant to imply otherwise, but your last example won't (and shouldn't) compile with clang/gcc.
clang++: error: cannot assign to variable 'b' with const-qualified type 'const somestruct *const'
g++: error: assignment of member ‘somestruct::moo’ in read-only object
Re: Overview of JavaScript ES6 features
#218For those using Babel already or want to use ES6+ on a set of supported browsers: we have started work on https://github.com/babel/babel-preset-env . Would appreciate more testing! It allows passing in a set of supported browsers and transpiling what is required using the lowest common denominator env (uses https://github.com/kangax/compat-table for data). // .babelrc with preset options { "presets": [ ["env", { "tar…
Wow, this is really excellent. Definitely will give this a shot!
Re: Overview of JavaScript ES6 features
#219Earlier quoted context omitted.
Honest question here --- What is the difference between let and global variables? There are hundreds of articles written about the doom associated with PHP globals, but let appears to be universally lauded. I must be missing something, but I can't tell where.
It's spelled out pretty well in the article. But if you want another example, consider these two code blocks: var foo; var bar; { let foo = "hello"; var bar = "world"; } console.log(foo); console.log(bar); This produces: undefined world The reason being that the `let` statement restricted that variable to the block it was in (defined by the { and }). `var` declares the variable globally, allowing it to be accessed ou…
"var" declares function scope, not global scope. If you really want global scope, declare the variable with no keyword preceding it (e.g. "foo = 3").
Re: Overview of JavaScript ES6 features
#220Please stop trying to fuck up javascript.