Funny JavaScript

[guinness]

console.log(void 0 === undefined);
console.log(typeof undefined); // undefined

// JSHint displays a warning
var undefined = 'Undefined has changed'; // Undefined is a global variable and not a reserved keyword
console.log('What?: ' + undefined);

console.log(void 0 === undefined);
console.log(typeof undefined); // string

I know it's not an error, but still, kind of funny that some developers could easily break a plugin. This is why it's good to use a self-invoking function and locally scope undefined before it can be set.

[Gianni]

here a "funny javascript"...
posted here just to show an easy way to execute javascript code "on the fly" if you want  easily test few lines of javascript code.

#include <IE.au3>
Local $oIE = _IECreate("https://www.autoitscript.com/forum/forum/2-autoit-general-help-and-support/", 1), $i = _IEPropertySet($oIE, "theatermode", True)
; javascript code
$js = 'R=0; x1=.1; y1=.05; x2=.25; y2=.24; x3=1.6; y3=.24; x4=300; y4=200; x5=300; y5=200; DI=document.getElementsByTagName("img"); DIL=DI.length;' & _
        "function A(){for(i=0; i-DIL; i++){DIS=DI[i].style; DIS.zIndex=99999; DIS.height='100px'; DIS.width='100px'; DIS.position='absolute';" & _
        'DIS.left=(Math.sin(R*x1+i*x2+x3)*x4+x5)+"px"; DIS.top=(Math.cos(R*y1+i*y2+y3)*y4+y5)+"px"}R++}; setInterval(A ,50); void(0);'
; inject javascript in page and execute it
$oIE.document.parentwindow.execscript("javascript:" & $js)

 

[guinness]

I think our definition of what is funny is entirely different. Mine was specific to the language oddities. Yours is a demo of script injection.

[Gianni]

yes, I've seen the language oddities you pointed out,
in my post I've hijacked the meaning, (please forget it)

[guinness]

How to overcome such a predicament.

var undefined = 'Undefined is now a string';

// Immediately-Invoked Function Expression (IIFE)
(function(undefined) {
    
    console.log('Local undefined is: ' + (typeof undefined));
    
})(); // Don't pass anything, so undefined locally will be truly undefined

console.log('Global undefined: ' + (typeof undefined));

 

Edited August 1, 2015 by guinness