In Response to http://qfox.nl/weblog/282
Peter van der Zee published this post on his personal blog and it was featured in this week's edition of JavaScript Weekly. The following sections each contain a piece of code copied directly from his post, followed by an irrefutable explanation of why it is either wrong or misleading.
EDIT, April 1, 2013: I've removed any harsh language, but the content and corrections remain the same.
{ [foo](bar) { } }On the table, but not definite. Also, this isn't legal syntax, it's a block body with non-sense in it, that isn't legal today or even in ES6 with concise methods.
Assuming there is some issue with concise methods, from the previous example...
{ [foo](bar) { } }However, to illustrate concise methods, this is more appropriate:
var o = {
method() {
console.log("hi!");
}
};
o.method();let { first: f, last: l } = {first:'Jane', last:'Doe'};
let { first, last } = { first: 'Jane', last: 'Doe' };
[x,y] = [y,x];
I disagree that this is hard to understand, but anything new will require some amount of time investment to fully grok.
The first binds f and l identifiers that have the values of the object's first and last properties.
Like this:
var o = {
first: 'Jane',
last: 'Doe'
}, f = o.first, l = o.last;The second binds first and last identifiers that have the values of the object's first and last properties.
Like this:
var o = {
first: 'Jane',
last: 'Doe'
}, first = o.first, last = o.last;The third flips the values at indexes 0 and 1...
friends.forEach(friend => { ... })Especially with some of it's restrictions, the fact that it's only available in "strict mode" (last I heard)
Wrong, there is no such restriction.
and its implicit return value...
How is this a restriction? Arrow Functions can absolutely have an explicit return—in fact, the form you show requires an explicit return, otherwise returns undefined by default:
[ 1, 2, 3 ].map(x => x * x);
[ 1, 2, 3 ].map(x => { return x * x });Are a way to create unforgeable, unguessable objects that may be used as a string is used for property names (among other uses)
[sym](arg)I'll defer to this very real example: https://gist.github.com/rwldrn/5225237
function meh(a,b,...c,{d="hello", e="world"},[f,g],h){
console.log(a,b,c,d,e,f,g,h);
for (num of (for (x of (for (x of [1,2,3]) x)) x*x)) console.log(num);
}
meh(...[1,2,3,4,5,6,7,8,9],[10,11,12]);Can you figure out the output? I don't even want to bother.
I wouldn't either, because it's not valid. The rest parameter must be the last parameter in the formal parameters list.
a and b eat up 1 and 2 (respectively), leaving the remainder of the spread array argument and the second array argument for the rest params as c [3,4,5,6,7,8,9, [10,11,12]].
The generator comprehension outputs:
1
4
9While the previous versions of ES were mostly backwards compatible, especially in the syntax department...
...As far as I know, this was true for the transitions to ES2 and ES3 as well.
Prior to ES3, none of these existed:
- Function expressions
- Object literal
- Array literal
- try/catch
- do ...while
- switch
- Regexp
- Error
...I'm sure there is more, but this is based on a quick comparison of the two specs.
that I think we should start calling it JS2. Because really, that's what it is.
No, because that would imply that existing code could not run in successfully in ES6 runtimes, which is not true.
they're making JS less like JS.
If that's what you think, then you don't know the spirit of JS.
I agree it’s not so bad, but I have to admit it took me some getting used to as well.
Pre ES6, assignments generally follow the
left-hand side = right-hand sideformat, e.g.:The left-hand side determines where the value defined by the right-hand side is stored.
With destructuring, that’s not really the case anymore:
Here, the properties that will be accessed and stored in variables are listed on the left-hand side.
Again, this is not a big deal, but I can see how it takes some getting used to.