JSCrush 'reverse engineering'

jscrush-compress-pseudo.js

segmentLengthBound = ... // B, originally set to s.length/2
counter = {} // o
bestSavings = 0 // M
maxRepetitions = 0 // N
bestSegment = 0 // e
longestSegmentLength = 0 // Z
segmentLength = 0 // t

while (segmentLength <= segmentLengthBound) {
	start = 1;
	while (i < s.length-segmentLength) {
		j = start
		segment = s.substr(j, segmentLength);
        if (!counter[segment]) {
        	j = s.indexOf(segment, j + segmentLength)
            if (~j) {
            	longestSegmentLength = segmentLength
            	counter[segment] = 1
            	while (~j) {
            		j = s.indexOf(segment, j + segmentLength)
            		counter[segment]++
                }
            }
        }
        ++i
    }
    ++segmentLength
}

segmentLengthBound = longestSegmentLength

for (segment in counter) {
    segmentLength = encodeURI(i).replace(/%../g,'i').length // j
    repetitions = counter[segment]
    savings = repetitions * segmentLength - (repetitions + segmentLength + 1)
    if (savings > bestSavings || savings == bestSavings && repetitions > maxRepetitions) {
    	bestSavings = savings
    	maxRepetitions = repetitions
    	bestSegment = segment
    }
}

jscrush-end.js

for(Y=0;$="WVPKGFEDA@5#	
"[Y++];)
  with(_.split($))
    _=join(pop());
eval(_)

jscrush-minified.js

b.innerHTML="Javascript ❤ source<br><textarea rows=12 cols=80></textarea><br><button>CRUSH</button> <b></b><br><textarea rows=12 cols=80></textarea>"+b.innerHTML;Q=[];for(i=127;--i;i-10&&i-13&&i-34&&i-39&&i-92&&Q.push(String.fromCharCode(i)));setTimeout("b.children[1].value=eval(b.children[9].innerHTML.replace(/eval\\(_\\)/,'_'));L()");b.children[3].onclick=L=function(s){i=s=b.children[1].value.replace(/([\r\n]|^)\s*\/\/.*|[\r\n]+\s*/g,'').replace(/\\/g,'\\\\'),B=s.length/2,m='';for(S=encodeURI(i).replace(/%../g,'i').length;;m=c+m){for(c=0,i=122;!c&&--i;!~s.indexOf(Q[i])&&(c=Q[i]));if(!c)break;for(o={},M=N=e=Z=t=0;++t<=B;)for(i=0;++i<s.length-t;)if(!o[x=s.substr(j=i,t)])if(~(j=s.indexOf(x,j+t)))for(Z=t,o[x]=1;~j;o[x]++)j=s.indexOf(x,j+t);B=Z;for(i in o){j=encodeURI(i).replace(/%../g,'i').length;if(j=(R=o[i])*j-R-j-1)if(j>M||j==M&&R>N)M=j,N=R,e=i}if(!e)break;s=s.split(e).join(c)+c+e}c=s.split('"').length<s.split("'").length?(B='"',/"/g):(B="'",/'/g);i=b.children[6].value='_='+B+s.replace(c,'\\'+B)+B+';for(Y=0;$='+B+m+B+'[Y++];)with(_.split($))_=join(pop());eval(_)';i=encodeURI(i).replace(/%../g,'i').length;b.children[4].innerHTML=S+'B to '+i+'B ('+(i=i-S)+'B, '+((i/S*1e4|0)/100)+'%)'}

jscrush-original.js

_="b=\"Javascript ❤ sourceCRUSH</ <b></b>\"+b;Q=[]@127;Vi-1013343992Q.push(Strg.fromCharCode(i)setTimeout(\"1=e(9]Ae(_)/,'_'L()\");3].onclick=L=function(s){D1A(|^)s*//.*|+s*EAE,B=s/2,m'@S
;m=c+m){c=0,122;!cV!~Q)(c=Q!co={},M=N=e=Z=t=0;Ft<=B;)0;Fi<s-t;)!#=s.substr(Gi,t)])~())Z=t,#]=1;~j;#]F);B=Z@i  o){j
G(R=o)*j-R-j-1)j>M||G=MR>N)M=j,N=R,e=i}!eDs	e).Wc)+c+e}c=s	'\"E<s	\"'\")?(B\"',/\"/g):(B=\"'\",/'/g);6_sc,'KB)'@Y=0;$m'[YF];)with(_	$))_=Wpop(e(_)';i
4]=S5 to Ki5 (K(i-S)5, K((i/S*1e4|0)/100)+'%)'}
=encodeURI(i)A%..iE;b.childPn[ rowD12 colD80></>.Pplace(.nerHTML.lengthfor(\\	.split(s.dexOf(].ueif(i-Gx,j+t)textaPa));val+B+/g,'button>)bPak;i=in<br><[rn]&&='[i]#o[x5+'B@;A/Ds=E')F++Gj=K'+PreV--i;Wjo(";for(Y=0;$="WVPKGFEDA@5#	
"[Y++];)with(_.split($))_=join(pop());eval(_)

jscrush-reformat.js

b.innerHTML="Javascript ❤ source<br><textarea rows=12 cols=80></textarea><br><button>CRUSH</button> <b></b><br><textarea rows=12 cols=80></textarea>"+b.innerHTML;
Q=[];

for(i=127;--i;i-10&&i-13&&i-34&&i-39&&i-92&&Q.push(String.fromCharCode(i)))
    ;

setTimeout(function() {
    b.children[1].value = b.children[9].innerHTML;
    L()
});
b.children[3].onclick = L = function(s) {
    i = s = b.children[1].value.replace(/([\r\n]|^)\s*\/\/.*|[\r\n]+\s*/g,'').replace(/\\/g,'\\\\');
    B=s.length/2;
    m='';
    for(S=encodeURI(i).replace(/%../g,'i').length;;m=c+m) {
        for (c=0,i=122;!c&&--i;!~s.indexOf(Q[i])&&(c=Q[i]))
            ;
        if (!c)
            break;
        for (o={},M=N=e=Z=t=0; ++t<=B; )
            for (i=0;++i<s.length-t;)
                if (!o[x=s.substr(j=i,t)])
                    if (~(j=s.indexOf(x,j+t)))
                        for (Z=t,o[x]=1;~j;o[x]++)
                            j=s.indexOf(x,j+t);
        B=Z;
        for (i in o) {
            j=encodeURI(i).replace(/%../g,'i').length;
            if (j=(R=o[i])*j-R-j-1)
                if(j>M||j==M&&R>N)
                    M=j,N=R,e=i
        }

        if (!e)
            break;
        s=s.split(e).join(c)+c+e
    }
    c = s.split('"').length < s.split("'").length ? (B='"',/"/g) : (B="'",/'/g);
    i = b.children[6].value= '_=' + B + s.replace(c,'\\'+B) +B + ';for(Y=0;$=' + B + m + B + '[Y++];)with(_.split($))_=join(pop());eval(_)';
    i = encodeURI(i).replace(/%../g,'i').length;
    b.children[4].innerHTML = S + 'B to ' + i + 'B (' + (i=i-S) + 'B, ' + ((i/S*1e4|0)/100)+'%)'
}