Here is one example:

eval(function(p,a,c,k,e,d){e=function(c){return(c<a?'':e(parseInt(c/a)))+((c=c%a)>35?String.fromCharCode(c+29):c.toString(36))};if(!''.replace(/^/,String)){while(c--){d[e(c)]=k[c]||e(c)}k=[function(e){return d[e]}];e=function(){return'\\w+'};c=1};while(c--){if(k[c]){p=p.replace(new RegExp('\\b'+e(c)+'\\b','g'),k[c])}}return p}('4.h={H:9(d){T 7.F(9(){g 1=7;1.3={8:4(d.8,7),i:4(d.i,7),m:4.z.J(7),5:d.5,t:d.t,j:d.j,K:d.K,b:d.b,A:d.A};4.h.s(1,0);4(S).v(\'W\',9(){1.3.m=4.z.J(1);4.h.s(1,0);4.h.E(1)});4.h.E(1);1.3.8.v(\'O\',9(){4(1.3.t,7).l(0).a.I=\'P\'}).v(\'R\',9(){4(1.3.t,7).l(0).a.I=\'11\'});4(Z).v(\'10\',9(e){g p=4.z.Y(e);g c=0;k(1.3.b&&1.3.b==\'L\')g r=p.x-1.3.m.x-(1.w-1.3.5*1.3.8.n())/2-1.3.5/2;u k(1.3.b&&1.3.b==\'N\')g r=p.x-1.3.m.x-1.w+1.3.5*1.3.8.n();u g r=p.x-1.3.m.x;g M=B.G(p.y-1.3.m.y-1.X/2,2);1.3.8.F(9(q){6=B.Q(B.G(r-q*1.3.5,2)+M);6-=1.3.5/2;6=6<0?0:6;6=6>1.3.j?1.3.j:6;6=1.3.j-6;C=1.3.A*6/1.3.j;7.a.D=1.3.5+C+\'f\';7.a.o=1.3.5*q+c+\'f\';c+=C});4.h.s(1,c)})})},s:9(1,c){k(1.3.b)k(1.3.b==\'L\')1.3.i.l(0).a.o=(1.w-1.3.5*1.3.8.n())/2-c/2+\'f\';u k(1.3.b==\'o\')1.3.i.l(0).a.o=-c/1.3.8.n()+\'f\';u k(1.3.b==\'N\')1.3.i.l(0).a.o=(1.w-1.3.5*1.3.8.n())-c/2+\'f\';1.3.i.l(0).a.D=1.3.5*1.3.8.n()+c+\'f\'},E:9(1){1.3.8.F(9(q){7.a.D=1.3.5+\'f\';7.a.o=1.3.5*q+\'f\'})}};4.V.U=4.h.H;',62,64,'|el||fisheyeCfg|jQuery|itemWidth|distance|this|items|function|style|halign|toAdd|options||px|var|iFisheye|container|proximity|if|get|pos|size|left|pointer|nr|posx|positionContainer|itemsText|else|bind|offsetWidthiUtil|maxWidth|Math|extraWidth|width|positionItems|each|pow|build|display|getPosition|valign|center|posy|right|mouseover|block|sqrt|mouseout|window|return|Fisheye|fn|resize|offsetHeight|getPointer|document|mousemove|none'.split('|'),0,{}))

Obviously, this code is intentionally written to confuse other people. How can I understand it and rewrite it in simple code?

Is there some tool for this job? This is very common in HTML.

Here is one example:

eval(function(p,a,c,k,e,d){e=function(c){return(c<a?'':e(parseInt(c/a)))+((c=c%a)>35?String.fromCharCode(c+29):c.toString(36))};if(!''.replace(/^/,String)){while(c--){d[e(c)]=k[c]||e(c)}k=[function(e){return d[e]}];e=function(){return'\\w+'};c=1};while(c--){if(k[c]){p=p.replace(new RegExp('\\b'+e(c)+'\\b','g'),k[c])}}return p}('4.h={H:9(d){T 7.F(9(){g 1=7;1.3={8:4(d.8,7),i:4(d.i,7),m:4.z.J(7),5:d.5,t:d.t,j:d.j,K:d.K,b:d.b,A:d.A};4.h.s(1,0);4(S).v(\'W\',9(){1.3.m=4.z.J(1);4.h.s(1,0);4.h.E(1)});4.h.E(1);1.3.8.v(\'O\',9(){4(1.3.t,7).l(0).a.I=\'P\'}).v(\'R\',9(){4(1.3.t,7).l(0).a.I=\'11\'});4(Z).v(\'10\',9(e){g p=4.z.Y(e);g c=0;k(1.3.b&&1.3.b==\'L\')g r=p.x-1.3.m.x-(1.w-1.3.5*1.3.8.n())/2-1.3.5/2;u k(1.3.b&&1.3.b==\'N\')g r=p.x-1.3.m.x-1.w+1.3.5*1.3.8.n();u g r=p.x-1.3.m.x;g M=B.G(p.y-1.3.m.y-1.X/2,2);1.3.8.F(9(q){6=B.Q(B.G(r-q*1.3.5,2)+M);6-=1.3.5/2;6=6<0?0:6;6=6>1.3.j?1.3.j:6;6=1.3.j-6;C=1.3.A*6/1.3.j;7.a.D=1.3.5+C+\'f\';7.a.o=1.3.5*q+c+\'f\';c+=C});4.h.s(1,c)})})},s:9(1,c){k(1.3.b)k(1.3.b==\'L\')1.3.i.l(0).a.o=(1.w-1.3.5*1.3.8.n())/2-c/2+\'f\';u k(1.3.b==\'o\')1.3.i.l(0).a.o=-c/1.3.8.n()+\'f\';u k(1.3.b==\'N\')1.3.i.l(0).a.o=(1.w-1.3.5*1.3.8.n())-c/2+\'f\';1.3.i.l(0).a.D=1.3.5*1.3.8.n()+c+\'f\'},E:9(1){1.3.8.F(9(q){7.a.D=1.3.5+\'f\';7.a.o=1.3.5*q+\'f\'})}};4.V.U=4.h.H;',62,64,'|el||fisheyeCfg|jQuery|itemWidth|distance|this|items|function|style|halign|toAdd|options||px|var|iFisheye|container|proximity|if|get|pos|size|left|pointer|nr|posx|positionContainer|itemsText|else|bind|offsetWidthiUtil|maxWidth|Math|extraWidth|width|positionItems|each|pow|build|display|getPosition|valign|center|posy|right|mouseover|block|sqrt|mouseout|window|return|Fisheye|fn|resize|offsetHeight|getPointer|document|mousemove|none'.split('|'),0,{}))

Obviously, this code is intentionally written to confuse other people. How can I understand it and rewrite it in simple code?

Is there some tool for this job? This is very common in HTML.

• javascript
• html
• obfuscation
• deobfuscation

• 2 jsbeautifier.org – Alec Gorge Commented Nov 11, 2011 at 23:01
• 2 You can try Dean Edward's decoder; this code has been encoded with his tool. – pimvdb Commented Nov 11, 2011 at 23:08

4 Answers 4

This is not "encrypted", it is just obfuscated.

Yes, there are tools available to help, but it isn't a perfect process. All of the original variable names and comments and what not are gone, so a tool can't really add that stuff back in. You have to figure out the details yourself, but a tool can make it easier.

I wish people would stop doing that. There's just no way to "encrypt" JavaScript. It's an exercise in futility (minification is good, but obfuscation is bad and useless)

That being said, try using JSBeautifier. It gives me the following result:

jQuery.iFisheye = {
    build: function (options) {
        return this.each(function () {
            var el = this;
            el.fisheyeCfg = {
                items: jQuery(options.items, this),
                container: jQuery(options.container, this),
                pos: jQuery.iUtil.getPosition(this),
                itemWidth: options.itemWidth,
                itemsText: options.itemsText,
                proximity: options.proximity,
                valign: options.valign,
                halign: options.halign,
                maxWidth: options.maxWidth
            };
            jQuery.iFisheye.positionContainer(el, 0);
            jQuery(window).bind('resize', function () {
                el.fisheyeCfg.pos = jQuery.iUtil.getPosition(el);
                jQuery.iFisheye.positionContainer(el, 0);
                jQuery.iFisheye.positionItems(el)
            });
            jQuery.iFisheye.positionItems(el);
            el.fisheyeCfg.items.bind('mouseover', function () {
                jQuery(el.fisheyeCfg.itemsText, this).get(0).style.display = 'block'
            }).bind('mouseout', function () {
                jQuery(el.fisheyeCfg.itemsText, this).get(0).style.display = 'none'
            });
            jQuery(document).bind('mousemove', function (e) {
                var pointer = jQuery.iUtil.getPointer(e);
                var toAdd = 0;
                if (el.fisheyeCfg.halign && el.fisheyeCfg.halign == 'center') var posx = pointer.x - el.fisheyeCfg.pos.x - (el.offsetWidth - el.fisheyeCfg.itemWidth * el.fisheyeCfg.items.size()) / 2 - el.fisheyeCfg.itemWidth / 2;
                else if (el.fisheyeCfg.halign && el.fisheyeCfg.halign == 'right') var posx = pointer.x - el.fisheyeCfg.pos.x - el.offsetWidth + el.fisheyeCfg.itemWidth * el.fisheyeCfg.items.size();
                else var posx = pointer.x - el.fisheyeCfg.pos.x;
                var posy = Math.pow(pointer.y - el.fisheyeCfg.pos.y - el.offsetHeight / 2, 2);
                el.fisheyeCfg.items.each(function (nr) {
                    distance = Math.sqrt(Math.pow(posx - nr * el.fisheyeCfg.itemWidth, 2) + posy);
                    distance -= el.fisheyeCfg.itemWidth / 2;
                    distance = distance < 0 ? 0 : distance;
                    distance = distance > el.fisheyeCfg.proximity ? el.fisheyeCfg.proximity : distance;
                    distance = el.fisheyeCfg.proximity - distance;
                    extraWidth = el.fisheyeCfg.maxWidth * distance / el.fisheyeCfg.proximity;
                    this.style.width = el.fisheyeCfg.itemWidth + extraWidth + 'px';
                    this.style.left = el.fisheyeCfg.itemWidth * nr + toAdd + 'px';
                    toAdd += extraWidth
                });
                jQuery.iFisheye.positionContainer(el, toAdd)
            })
        })
    },
    positionContainer: function (el, toAdd) {
        if (el.fisheyeCfg.halign) if (el.fisheyeCfg.halign == 'center') el.fisheyeCfg.container.get(0).style.left = (el.offsetWidth - el.fisheyeCfg.itemWidth * el.fisheyeCfg.items.size()) / 2 - toAdd / 2 + 'px';
        else if (el.fisheyeCfg.halign == 'left') el.fisheyeCfg.container.get(0).style.left = -toAdd / el.fisheyeCfg.items.size() + 'px';
        else if (el.fisheyeCfg.halign == 'right') el.fisheyeCfg.container.get(0).style.left = (el.offsetWidth - el.fisheyeCfg.itemWidth * el.fisheyeCfg.items.size()) - toAdd / 2 + 'px';
        el.fisheyeCfg.container.get(0).style.width = el.fisheyeCfg.itemWidth * el.fisheyeCfg.items.size() + toAdd + 'px'
    },
    positionItems: function (el) {
        el.fisheyeCfg.items.each(function (nr) {
            this.style.width = el.fisheyeCfg.itemWidth + 'px';
            this.style.left = el.fisheyeCfg.itemWidth * nr + 'px'
        })
    }
};
jQuery.fn.Fisheye = jQuery.iFisheye.build;

Other links (lifted from the very same page):

• Chrome: jsbeautify-for-chrome by Tom Rix,
• Chrome: Pretty Beautiful JavaScript by Will McSweeney,
• Firefox: Javascript deminifier by Ben Murphy, to be used together with the firebug,
• Safari: Safari extension by Sandro Padin,
• Opera: Readable JavaScript by Dither,
• Opera: Source extension by Deathamns,
• Fiddler proxy: JavaScript Formatter addon

Using one of the unpackers mentioned on this question:

• How to unpack the contents of a Javascript file?

you can unpack the packed javascript to the following code:

jQuery.iFisheye = {
    build: function (options) {
        return this.each(function () {
            var el = this;
            el.fisheyeCfg = {
                items: jQuery(options.items, this),
                container: jQuery(options.container, this),
                pos: jQuery.iUtil.getPosition(this),
                itemWidth: options.itemWidth,
                itemsText: options.itemsText,
                proximity: options.proximity,
                valign: options.valign,
                halign: options.halign,
                maxWidth: options.maxWidth
            };
            jQuery.iFisheye.positionContainer(el, 0);
            jQuery(window).bind('resize', function () {
                el.fisheyeCfg.pos = jQuery.iUtil.getPosition(el);
                jQuery.iFisheye.positionContainer(el, 0);
                jQuery.iFisheye.positionItems(el)
            });
            jQuery.iFisheye.positionItems(el);
            el.fisheyeCfg.items.bind('mouseover', function () {
                jQuery(el.fisheyeCfg.itemsText, this).get(0).style.display = 'block'
            }).bind('mouseout', function () {
                jQuery(el.fisheyeCfg.itemsText, this).get(0).style.display = 'none'
            });
            jQuery(document).bind('mousemove', function (e) {
                var pointer = jQuery.iUtil.getPointer(e);
                var toAdd = 0;
                if (el.fisheyeCfg.halign && el.fisheyeCfg.halign == 'center') var posx = pointer.x - el.fisheyeCfg.pos.x - (el.offsetWidth - el.fisheyeCfg.itemWidth * el.fisheyeCfg.items.size()) / 2 - el.fisheyeCfg.itemWidth / 2;
                else if (el.fisheyeCfg.halign && el.fisheyeCfg.halign == 'right') var posx = pointer.x - el.fisheyeCfg.pos.x - el.offsetWidth + el.fisheyeCfg.itemWidth * el.fisheyeCfg.items.size();
                else var posx = pointer.x - el.fisheyeCfg.pos.x;
                var posy = Math.pow(pointer.y - el.fisheyeCfg.pos.y - el.offsetHeight / 2, 2);
                el.fisheyeCfg.items.each(function (nr) {
                    distance = Math.sqrt(Math.pow(posx - nr * el.fisheyeCfg.itemWidth, 2) + posy);
                    distance -= el.fisheyeCfg.itemWidth / 2;
                    distance = distance < 0 ? 0 : distance;
                    distance = distance > el.fisheyeCfg.proximity ? el.fisheyeCfg.proximity : distance;
                    distance = el.fisheyeCfg.proximity - distance;
                    extraWidth = el.fisheyeCfg.maxWidth * distance / el.fisheyeCfg.proximity;
                    this.style.width = el.fisheyeCfg.itemWidth + extraWidth + 'px';
                    this.style.left = el.fisheyeCfg.itemWidth * nr + toAdd + 'px';
                    toAdd += extraWidth
                });
                jQuery.iFisheye.positionContainer(el, toAdd)
            })
        })
    },
    positionContainer: function (el, toAdd) {
        if (el.fisheyeCfg.halign) if (el.fisheyeCfg.halign == 'center') el.fisheyeCfg.container.get(0).style.left = (el.offsetWidth - el.fisheyeCfg.itemWidth * el.fisheyeCfg.items.size()) / 2 - toAdd / 2 + 'px';
        else if (el.fisheyeCfg.halign == 'left') el.fisheyeCfg.container.get(0).style.left = -toAdd / el.fisheyeCfg.items.size() + 'px';
        else if (el.fisheyeCfg.halign == 'right') el.fisheyeCfg.container.get(0).style.left = (el.offsetWidth - el.fisheyeCfg.itemWidth * el.fisheyeCfg.items.size()) - toAdd / 2 + 'px';
        el.fisheyeCfg.container.get(0).style.width = el.fisheyeCfg.itemWidth * el.fisheyeCfg.items.size() + toAdd + 'px'
    },
    positionItems: function (el) {
        el.fisheyeCfg.items.each(function (nr) {
            this.style.width = el.fisheyeCfg.itemWidth + 'px';
            this.style.left = el.fisheyeCfg.itemWidth * nr + 'px'
        })
    }
};
jQuery.fn.Fisheye = jQuery.iFisheye.build;

In this case, you can get the original source here: http://interface.eyecon.ro/download. It's not really "obfuscated", in that the goal wasn't really obfuscation; rather, the goal was "compression" (minification), and the tool for that was a compressor/obfuscator.

(Of course, the tools that everyone else mentions are indispensable here. I used jsbeautifier.org to find that the whole thing is an assignment to jQuery.iFisheye, which then told me what to Google to find the above.)