brianleroux / wtfjs

wtfjs.com!

    :::       :::::::::::::::::::::::::::::::::::::::::::
    :+:       :+:    :+:    :+:           :+:   :+:    :+:
    +:+       +:+    +:+    +:+           +:+   +:+
    +#+  +:+  +#+    +#+    :#::+::#      +#+   +#++:++#++
    +#+ +#+#+ +#+    +#+    +#+           +#+          +#+
     #+#+# #+#+#     #+#    #+#       #+# #+#   #+#    #+#
      ###   ###      ###    ###        #####     ########
      ---------------------------------------------------
      JavaScript code blog.

Share your wtfjs moment

It has never been easier to contribute a wtf to wtfjs.com!

• fork this repo
• add your wtf under src/shared/md (format: yyyy-mm-dd-title.md)
• don't forget to add your name and link to twitter/github at the bottom!
• send a pull request
• WTF

Example post format

```
Array(20).map(function(elem) { return 'a'; }); // Array of undefined x 20
```

More info [here](http://www.ecma-international.org/ecma-262/5.1/#sec-15.4.4.19).
Thanks [Paul Irish](https://twitter.com/paul_irish) for the explanation.

— [@yourtwitterhandle_or_githubhandle][1]

[1]:https://githubortwitter.com/yourusername

http://wtfjs.com was created by @brianleroux. Everything here is under the WTFPL 2.0 license.

---

Contributors

Ordered by date of first contribution. Auto-generated on Thu Aug 09 2012 19:07:44 GMT-0700 (PDT).

• Brian LeRoux aka brianleroux
• Oleg Slobodskoi aka kof
• Allen Pike aka akrabat
• Rémi Prévost aka remiprev
• rwldrn aka rwldrn
• Luke Andrews aka attaboy
• AJ ONeal aka coolaj86
• Kambfhase aka Kambfhase
• Thomas Fuchs aka madrobby
• Arnout Kazemier aka 3rd-Eden
• Bradley Meck aka bmeck
• airportyh aka airportyh
• Diogo Baeder de Paula Pinto aka diogobaeder
• Peter Galiba aka Poetro
• Dan Beam aka danbeam
• David Trejo aka DTrejo
• Jakub Vrana aka vrana
• Bodo Tasche aka bitboxer
• qfox aka qfox
• Johan Sundström aka johan
• Mathias Bynens aka mathiasbynens
• Ken Snyder aka kensnyder
• David Wolever aka wolever
• Brandon Benvie aka Benvie
• Stephen Belanger aka Qard
• Dan Lash aka danlash
• Pawel 'lord_T' Maruszczyk aka pawel
• David Chambers aka mikechambers
• Jamund Ferguson aka xjamundx
• Thaddee Tyl aka espadrine
• Stanley Stuart aka fivetanley
• Ben Combee aka unwiredben
• Gonçalo Morais aka gnclmorais
• Maxime Euzière aka xem

wtfjs's Issues

Regular Expression and Slash - not really an issue

What is described in the 2014-01-29-regular-expression-and-slash post is expected Regex behavior, not a JS WTF.

It's the same, for example, in C#, Python or Ruby.

Bug in "false isnt false"

In post "false isnt false":

true == 'true' // true

but my FF and Chrome say "false". Is it true: see http://www.ecma-international.org/ecma-262/5.1/#sec-11.9.3

The Hungry Variable

Again some misunderstanding
There is a small difference between

/[/ + "javascript"[0] + '///'

and

/[/ + "javascript"[0] + '///'

Missing document

Is it just me or is 2018-19-01-weird-number-addition.md missing from the overview?

wtfjs.com is down

down for everyone or just me™?

Website issues

Great to see the site back up again—I'd like to report a few issues I've noticed while browsing the site.

• The first entry on https://wtfjs.com/, "2016 03 19 wierd instanceof", leads to a page that just says "wtf! not found"

• You're not setting the charset to UTF-8. E.g. https://wtfjs.com/wtfs/2014-02-20-math-pow shows "— @123jimin" instead of "— @123jimin" in my browser

• https://wtfjs.com/wtfs/2013-12-15-charAt-is-not-the-same-as-[] is just an empty page

• https://wtfjs.com/wtfs/2010-04-31-isNaN links to https://wtfjs.com/2010/02/12/null-is-not-an-object which just shows {"message":"Missing Authentication Token"} The link should be https://wtfjs.com/wtfs/2010-02-12-null-is-not-an-object

• https://wtfjs.com/wtfs/2015-04-23-screwy-negative-array-index is missing newlines

all your commas are belong to Array last WTF

The last WTF:

",,," == Array((null,'cool',false,NaN,4)); // true

can be explained in the following way:

1. The expression (null,'cool',false,NaN,4) being evaluated first
2. Comma "," operator executes both sides of expression and returns the result of the last one, so

 null, 'cool', false, NaN, 4 => 'cool', false, NaN, 4 => false, NaN, 4 => NaN, 4 => 4

3. So the remaining expression is the same as one of the explained cases:

 ",,," == new Array(4); // true

So really, it's just some magic behind the comma operator.

Not so infinite loop

n = 0; while (Math.pow(2, n) < Math.pow(2, n) + 1) { n++; }

Posts Sorting Issue ...

Since readdir doesn't guarantee the order of returned filenames there are two missing calls to sort() in the code of post.js.

--- a/node-code-blog/post.js
+++ b/node-code-blog/post.js
@@ -25,3 +25,3 @@ Post.paginate = function(page) {
     fs.readdir(postsPath, function(err, files){
-        var posts = Post.all(files).reverse()
+        var posts = Post.all(files.sort().reverse())
         ,   count = 5
@@ -52,3 +52,3 @@ Post.rss = function(title, desc, domain) {
     s += 'http://' + domain + '/'; 
-    var posts = Post.all(fs.readdirSync(postsPath).reverse());
+    var posts = Post.all(fs.readdirSync(postsPath).sort().reverse());
     for (var i = 0; i < 5; i++) {        

showdown should be npm module

eh

es5

var a = [1,2,3];
Array.prototype.isPrototypeOf(a); // true
var b = 123;
Number.prototype.isPrototypeOf(b); // false
var c = new Number(123);
Number.prototype.isPrototypeOf(b); // true
typeof b; //number
typeof c; //object
b == c; //true
b === c; //false
c += 1; //124
typeof c; //number

typeof null; //object

RSS is broken

You better fix your RSS feed, cause it's totally broken...

regards

enhance.dev rework

Todo:

• / currently redirects to /wtfs. That's not the current behavior
• /wtfs works but /wtfs doesn't. That's not the current behavior
• about and license page

Open questions

• jQuery still needed? I can't find any place, where it is used
• Should the design stay the same or be brought up to date?
• Should shared/ logic be preserved?

Fix syntax highlighting

On at least some Markdown processors, the line containing "```" can contain the language, such as:

``` javascript
function code() {yield 5; return null;}
```

Could display as

function code() {yield 5; return null;}

This means that one potential solution to fixing the syntax highlighting is to simply add the "javascript" language specification on the initial "```" line. Please check whether it actually works for your posts already, or if some additional plugin to support the Javascript language is needed.

EDIT: This page already has that fix. You should try to install a syntax highlighting plugin to your Markdown install and check on this page, before making this change. Perhaps highlight.js?

EDIT 2: See this page for how to enable syntax highlighting with Marked.JS.

Maintain this repository

Hello everybody,

This repository seems to be inactive for a quite long time. It has 13 open issues and 35 Pull Requests. That's why I create a new github organization to fork and maintain this repository.
Here is it: https://github.com/wthjs/wtfjs

If you want to maintain this repository, please let know by leaving comment on this issue.

Thanks.

https://wtfjs.com/wtfs/2013-03-06-false-isnt-false

https://wtfjs.com/wtfs/2013-03-06-false-isnt-false

It seems like this has since been changed, or it was not accurate.
It also contradicts this one.
https://wtfjs.com/wtfs/2013-04-18-true-story-bro

If it helps I can create a PR to remove it/ Update it to say it no longer applies.

operator if'

if (-1 && -100 && 100) console.log('wtf?')

x

syntax highlight sucks nuts

need a better solution

"native" is an undocumented reserved word on Android 2.2

yes.

RSS broken

http://wtfjs.com/rss

This page contains the following errors:

error on line 19 at column 14: Opening and ending tag mismatch: code line 0 and p
Below is a rendering of the page up to the first error.

Arary Comparison

http://wtfjs.com/2013/01/28/array-comparison
'Did you know that JavaScript can compare arrays using lexicographical ordering?'

With >, >=, <, <=, they're both converted to strings, and JavaScript will compare each character code in order. Note also,

[10, 2, 3] > [2, 2, 3] // false

Fibonacci is so last year, let's go with Lucas numbers.

Made by hand, rather than using wtfjs, but I'm sure it's easy to redo:

function lucas(n) { for(_=++[+[]][+[]],__=++[_][+[]]<<++[_][+[]]<<++[_][+[]]<<_;__>+[];_=++[+[]][+[]]+(++[+[]][+[]]/_),__--);for(__=_;-++[+[]][+[]]+--n;_*=__);return(++[+[]][+[]]/++[++[+[]][+[]]][+[]]+_)|+[]; }

Computes the golden ratio φ by evaluating the continued fraction for the golden ratio over 64 iterations, then computes the Lucas number lucas(n) directly as round(φ^(n-1)).

(more detailed composition explained over at https://pomax.github.io/#gh-weblog-1418775170598)

JSON.stringify(Infinity) goes crazy

JSON.stringify(Infinity) === "null" // Of course, I know that the space is non-finite and mostly empty but I just want the string

No recursive function in strict mode

[code=es:0]
"use strict";

var foo, bar, baz;

foo = function(bar){
if(bar === 0){
return(1);
}else if(bar < 0){
return(-1);
}else{
return(bar * arguments.callee(bar - 1));
}
}

foo(5);
[/code]

Does not work in strict mode, throws a type error.

Array.prototype.indexOf WTF or not empty array don't contain it element.

Not empty array don't contains it element:
var a = [,]; alert(a.indexOf(a[0]));

alert will return -1. The main point in this example is difference between uninitialized and undefined values.

The problem is in this:
a.length is 1. So array has some elements. But a[0] is undefined and a.indexOf(undefined) will return -1.

Undefined is the javascript primitive type. Uninitialized means the value that don't have any javascript type.

P.S. I'm trying to find why a[0] return undefined now for complete explanation.

Comma operator plus Parentheses plus Assignment plus Increment

Never mind sorry

x

[interesting?] Was Javascript really made in 10 days?

https://buttondown.email/hillelwayne/archive/did-brendan-eich-really-make-javascript-in-10-days/

new Number()

var x = 12;
var y = 12;
x === y // true

var x = new Number(12);
var y = new Number(12);
x === y // false
x == y // false

var x = y = new Number(12);
x === y // true

While it might be useful to set two variables as references to the same Number instance object, the object instance does not have any method available to mutate it's internal primitive value, so this feature ended up only useful in confusing people.

Probably something inherited from Java?

Explanation for why-am-i-a-number

why am i a number by @jhnns:

Can someone tell me?

"Why am I a " + typeof + ""; // "Why am I a number"

Because in this context the (second) + character isn't an addition operator but a unary + operator.

It is used to cast values to a number. In this case the empty string is casted to the number 0, of which the type is (obviously) "number".

Remember about +new Date()? This +"" is just like that.

So wrapped in logical groups:

"Why am I a " + ( typeof ( +"" ) ); // "Why am I a number"

Website down

Hi guys,
looks like the website is down?

The last time I tried it just showed "nginx correctly installed"?

It might be a good idea to set it up on github.io?

Date comparison

I'm surprised no one uncovered that here:

new Date(10) == new Date(10) // false
new Date(10) < new Date(11) // true
new Date(11) > new Date(12) // false
new Date(11) > new Date(10) // true

Two object instances are always unequal. But they decided to overload operator < and > for Date and not ==. This renders the whole thing useless.

Unschareable URL

http://wtfjs.com/2013/08/07/Math.max()-behaviour isn't schareable on twitter. 😭

Is this project dead?

Lots of pull requests which hasn't been merged and the website hasn't been updated since 2016

Page does not load (400 error)

This page is in the index, but actually attempting to open it leads to a 400 error. Is it related to the parsing of the URL seeing "[]" as a trouble input and bailing out due to what it considered a security issue?

EDIT: The link on this issue is mangled and the right brackets are percent-encoded which leads to a 404 not found error. Perhaps move the page?

true == 'true' is not true

The section "false isnt false" claims that:

true == 'true'     // true
false == 'false';  // false

But in fact the first line also resolves to false. Please correct it!

You may prefer to write that section like this:

false == '0';      // true
false == 'false';  // false

typo

Hi again, I'm sorry but there are 3 typos in my last post "hexadecimal weirdness"

Can you put
"In JS you can represent numbers in hexadecimal, right?"
instead of
"In JS you an represent numbers in haxadecimal, right?"

and

alert(hex.toString(16)); // 0xFF5500
instead of
alert(hex.toString(16); // 0xFF5500

Thanks!

Regexp: Not exactly reusable...

I think this is just WTF.

[jann@Jann-PC dnode-protocol master]$ node
> var regexp = /\+((?:\+)?[\w\-]+)*(?:\.v\d+\.\d+\.\d+)?(?:\.js)$/g;
> function f(){console.log(regexp.exec('/socket.io+websocket.v0.8.10.js') != null);}
> setInterval(f, 100)
{ ontimeout: [Function] }
> true
false
true
false
true
false
true
false