Inspired by JSFuck, but here's the rules:
[a-zA-Z0-9]), no spaces, only `` quotes
Use either `${<code>}` or (<code>+[]) to obtain useful keywords:
| keyword | code |
|---|---|
[object Object] | {} |
true | !`` |
false | ![] |
NaN | -`!` |
undefined | [][[]] |
-Infinity | ~[]/[] |
| number | code |
|---|---|
| -4 | ~-~-~!`` |
| -3 | ~-~!`` |
| -2 | ~!`` |
| -1 | ~`` |
| -0 | -`` |
| 0 | +`` |
| 1 | +!`` |
| 2 | -~!`` |
| 3 | -~-~!`` |
| 4 | -~-~-~!`` |
We can use variables, but only those whose name contains `$` and `_` so we'll use some sort of morse code-based encoding, with `$`⇒`.` and `_`⇒`-`, and a prefix to differentiate lowercase and uppercase:
| code | |
|---|---|
| a | $$_=`${![]}`[+!``] |
| b | $_$$$=`${{}}`[-~!``] |
| c | $_$_$=`${{}}`[-~-~-~-~!``] |
| d | $_$$=`${[][[]]}`[-~!``] |
| e | $$=`${!``}`[-~-~!``] |
| f | $$$_$=`${![]}`[-``] |
| i | $$$=`${[][[]]}`[-~-~-~-~!``] |
| j | $$___=`${{}}`[-~-~!``] |
| l | $$_$$=`${![]}`[-~!``] |
| n | $_$=`${[][[]]}`[+!``] |
| o | $___=`${{}}`[+!``] |
| r | $$_$=`${!``}`[+!``] |
| s | $$$$=`${![]}`[-~-~!``] |
| t | $_=`${!``}`[-``] |
| u | $$$_=`${!``}`[-~!``] |
| y | $_$__=`${-~[]/[]}`[-~-~-~-~-~-~!``] |
| I | _$$=`${~[]/[]}`[+!``] |
| N | __$=``${-`!`}`[-``] |
| O | ____=`${{}}`[-~-~-~-~-~-~-~!``] |
| space | ____$=`${{}}`[-~-~-~-~-~-~!``] |
Actually, we can just use the [a,b]=“ab” notation to make it way shorter. Note that using +[] or +`` is now shorter due to the lack of need of parentheses.
[,$___,$_$$$,$$___,$$,$_$_,$_,____$,____]={}+[], // o,b,j,e,c,t,space,O [$$$_$,$$_,$$_$$,$$$$]=![]+[], // f,a,l,s [,$$_$]=!``+[], // r [__$]=-`!`+[], // N [,_$$,$_$,,$$$,,,,$_$__]=~[]/[]+[], // I,n,i,y [$$$_,,$_$$]=[][[]]+[] // u,d
Of course, a few of those are not needed, and can be removed if you don't need them, and those identifiers can always be shorter. We need at least enough to spell constructor and return btoa. Here's the minimum:
[,$___,$_$$$,,$$,$_$_$,$_,____$]={}+[], // o,b,e,c,t,space [,$$_,,$$$$]=![]+[], // a,s [,$$_$]=!``+[], // r [$$$_,$_$]=[][[]]+[], // u,n
Now we have enough letters to execute arbitrary code:
$=(_=>_)["constructor"] // returns Function
$=(_=>_)[$_$_$+$___+$_$+$$$$+$_+$$_$+$$$_+$_$_$+$_+$___+$$_$]
We can then use `btoa` to get a lot of the letters we're missing:
[K,i,g,h]=Function("return btoa")()(`*(!`) // returns 'Kigh'
[,$$$,$__$,$$$$$]=$($$_$+$$+$_+$$$_+$$_$+$_$+____$+$_$$$+$_+$___+$$_)()(`*(!`)
_=Function("return this")()
_=$($$_$+$$+$_+$$$_+$$_$+$_$+____$+$_+$$$$$+$$$+$$$$)()
_["console"]["log"]("hello")
_[$_$_$+$___+$_$+$$$$+$___+$$_$$+$$][$$_$$+$___+$__$]($$$$$+$$+$$_$$+$$_$$+$___)
[,$___,$_$$$,,$$,$_$_$,$_,____$]={}+[], // o b e c t space [,$$_,$$_$$,$$$$]=![]+[], // a l s [,$$_$]=!``+[], // r [$$$_,$_$]=[][[]]+[], // u n $=(_=>_)[$_$_$+$___+$_$+$$$$+$_+$$_$+$$$_+$_$_$+$_+$___+$$_$], // $=Function [,$$$,$__$,$$$$$]=$($$_$+$$+$_+$$$_+$$_$+$_$+____$+$_$$$+$_+$___+$$_)()(`*(!`) // i g h $($$_$+$$+$_+$$$_+$$_$+$_$+____$+$_+$$$$$+$$$+$$$$)() // $("return this")() [$_$_$+$___+$_$+$$$$+$___+$$_$$+$$][$$_$$+$___+$__$]($$$$$+$$+$$_$$+$$_$$+$___) // console.log("hello")
[,$___,$_$$$,,$$,$_$_$,$_,____$]={}+[],[,$$_,$$_$$,$$$$]=![]+[],[,$$_$]=!``+[],[$$$_,$_$]=[][[]]+[],$=(_=>_)[$_$_$+$___+$_$+$$$$+$_+$$_$+$$$_+$_$_$+$_+$___+$$_$],[,$$$,$__$,$$$$$]=$($$_$+$$+$_+$$$_+$$_$+$_$+____$+$_$$$+$_+$___+$$_)()(`*(!`),$($$_$+$$+$_+$$$_+$$_$+$_$+____$+$_+$$$$$+$$$+$$$$)()[$_$_$+$___+$_$+$$$$+$___+$$_$$+$$][$$_$$+$___+$__$]($$$$$+$$+$$_$$+$$_$$+$___)