I need a regex or something to remove this kind of comments.
/*!
* Foo Bar
*/
I tried with /(\/*!.**\/)/m but fails. Any Suggestion?
7 Answers
To do it accurately and efficiently, there is a better regex:
regexp = /\/\*![^*]*\*+(?:[^*\/][^*]*\*+)*\//
result = subject.gsub(regexp, '')
Jeffrey Friedl covers this specific problem at length (using C-comments as an example) in his classic work: Mastering Regular Expressions (3rd Edition). Here is a breakdown of the regex which illustrates the "Unrolling-the-Loop" efficiency technique.
regexp_long = / # Match she-bang style C-comment
\/\*! # Opening delimiter.
[^*]*\*+ # {normal*} Zero or more non-*, one or more *
(?: # Begin {(special normal*)*} construct.
[^*\/] # {special} a non-*, non-\/ following star.
[^*]*\*+ # More {normal*}
)* # Finish "Unrolling-the-Loop"
\/ # Closing delimiter.
/x
result = subject.gsub(regexp_long, '')
Note that this regex does not need Ruby's 'm' dot-matches-all modifier because it does not use the dot!
Additional: So how much more efficient is this regex over the simpler /\/\*!.*?\*\//m expression? Well using the RegexBuddy debugger, I measured how many steps each regex took to match a comment. Here are the results for both matching and non-matching: (For the non-,matching case I simply removed the last / from the comment)
/*!
* This is the example comment
* Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar
* Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar
* Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar
*/
'
REGEX STEPS TO: MATCH NON-MATCH
/\/\*!.*?\*\//m 488 491
/\/\*![^*]*\*+(?:[^*\/][^*]*\*+)*\// 23 29
'
As you can see, the lazy-dot solution (which must backtrack once for each and every character in the comment), is much less efficent. Note also that the efficiency difference is even more pronounced with longer and longer comments.
CAVEAT Note that this regex will fail if the opening delimiter occurs inside a literal string, e.g. "This string has a /*! in it!". To do this correctly with 100% accuracy, you will need fo fully parse the script.
2 Comments
amitkaz
Wow. Clearly you put a lot of work into this answer, and it is a better solution.. but I think it's a case of premature optimization that over complicate the code.
ridgerunner
@amikazmi: For anyone who has studied and is familiar with: MRE3, this is the simple solution!
* has to be escaped, otherwise it matches zero or more occurences of / (in case of \/*). There is an syntax error as well in .**. Try the next RE with * properly escaped:
/\/\*!.*?\*\//m
Comments
1 Comment
ridgerunner
Note that
/(\/\*!.*\*\/)/m will fail if there is than one comment in the text. (The greedy-dot-star will match everything from the beginning of the first comment to the end of the last comment. For this expression to work, the dot-star must be lazy, i.e. .*?Simple regexps for removing (c-style) single-line and multi-line comments. But note that those are really simple - for example they don't take possibility of /* */ inside a string literal. But should be fine for removing comments from a simple code:
str.gsub!(/\/\*.*?\*\//m, '') # remove multiline comments
str.gsub!(/\s*\/\/.*/, '') # remove single-line comments
Comments
You could use a javascript compressor like YUI compress or Google Closure Compiler
Comments
Well i think i got what you want :)
<html>
<head>
<title>Code Condenser</title>
<style type="text/css">
#source{font-size:10pt;width:90%;height:300px;}
body{text-align:center;}
</style>
<script type="text/javascript">
function vc_js_condenser(){var a=/[a-zA-Z0-9._'"]/;var b=/[a-zA-Z0-9._]/;var c=/[a-zA-Z0-9._\]\)"']/;
function d(e,f){e=e.replace(/[\n\r]+/g,"\n");var g=(typeof(f)=="boolean")?f:false;var h=["var","else",
"new","do","case","with","typeof","delete","try","finally","throw","in","instanceof"];var i=0;var j=
new Array();var k=e.split('');l=k.length;var m=new Array();var G=null;var o=false;var p=[["'","'","\\"]
,['"','"','\\'],["//","\n",null],["/*","*/",null]];var q="[](){},;/\n";var r;function s(){if(m.length<1)
return;var u=m.join('');if((!g)||((u.match(/^\/\//)==null)&&(u.match(/^\/\*/)==null))){if(!((u=="\n")&&
((G==';')||(G=="\n")))){if((G!=null)&&(G.match(a)!=null)&&(u.match(a)!=null))j[j.length]=' ';j[j.length]
=u;G=u;}}m.length=0;v=false;}var v=false;var w=false;while(i<l){if(!o){if((k[i]==" ")||(k[i]=="\t")){s();
}else{var x=false;if(q.indexOf(k[i])>-1){if(k[i]!='/'){x=true;s();}else if((m.length>0)&&(m[0]!='/')){
s();}}for(var y=0;y<p.length;y++){var z='';if((m.length>0)&&(m[m.length-1]==p[y][0].charAt(0)))z=m[
m.length-1];var A=z+k[i];if(A==p[y][0]){o=true;r=y;if(z!='')m.length--;if(m.length>0)s();if(z!='')m
[m.length]=z;break;}}if((k[i]=="/")&&(!o)&&(m.length==0)&&(G!=null)&&(G.match(c)==null)&&(i+1<k.length)
&&(k[i+1]!='/')){o=true;r=null;}var B=k[i].match(b)!=null;if(m.length<1)v=B;if(v!=B){s();v=B;}m[m.length]
=k[i];if(x)s();}}else{m[m.length]=k[i];var C=m.join('');if(r!=null){var D=C.lastIndexOf(p[r][1]);if((D!=-1)
&&(D>0)){if(m[D-1]==p[r][2]){if((D>2)&&(m[D-2]==p[r][2])){s();o=false;}}else{s();o=false;}}}else{if((w==false)
&&(k[i]=="/")){i++;while((i<k.length)&&(k[i].match(b)!=null)){m[m.length]=k[i];i++;}s();o=false;i--;}else{if
(!w&&(k[i]=="\\"))w=true;else w=false;}}}i++;}s();var E=-1;for(var i=0;i<j.length;i++){var u=j[i];var
F=(i>0)?j[i-1]:null;var n=(i<(j.length-1))?j[i+1]:null;if(u=="\n"){if((F!=null)&&(n!=null)){if((F.match(c)
!=null)&&(n.match(a)!=null)){u=';';for(var H=h.length-1;H>-1;H--){if(F==h[H])u=' ';}j[i]=u;E++;if((E<j.length)
&&(E>-1)&&(i!=E))j[E]=j[i];}}}else{E++;if((E<j.length)&&(E>-1)&&(i!=E))j[E]=j[i];}}j.length=E+1;return j;}var
I=document.getElementById('source');var J=I.value.length;I.value=d(I.value,document.getElementById('uncomment').checked
==true).join('');var K=I.value.length;var F=document.getElementById("saved");F.removeChild(F.firstChild);var
L=document.createElement("span");F.appendChild(L);L.appendChild(document.createTextNode("Original Size: "+
J+" characters"));L.appendChild(document.createElement("br"));L.appendChild(document.createTextNode(
"Condensed Size: "+K+" characters"));L.appendChild(document.createElement("br"));L.appendChild(
document.createTextNode("Size Difference: "+(J-K)+" characters"));if(J!=0){L.appendChild(document.createElement
("br"));L.appendChild(document.createTextNode("Condensed Code is "+(Math.floor(K/J*10000)/100)+
"% of original size."));}}
</script>
</head>
<body>
<h1>JavaScript Source Code Condenser</h1>
<p>Paste only valid Javascript (no HTML tags) in the box below.</p>
<button onclick="vc_js_condenser();">Condense Code</button> <input type="checkbox" checked="checked" id="uncomment" />Remove Comments <button onclick="document.getElementById('source').select();">Select All</button><br />
<textarea id="source"></textarea><br />
<p id="saved"><span></span></p>
</body>
</html>
Kindly save this script as HTML and then run it in your browser then copy your javascript and put it in the texterea and then condense it with the button
This code will remove the spaces and comments on your code so please dont forget end your functions with ; to avoid syntax error.
This will help you reducing your javascript files size this will put ur javascript in 1 line , so if you need it back as well formed u can use this addon in firefox if u use it http://www.formatjavascript.com/
Regards :) please mark this answer as the correct one if u see it useful
Comments
I would highly suggest removing these comment with Google's Closure Compiler, I have used it in production and it's fantastic.
jsminor similar.var re = /funk\/*/;will your code be smart enough to ignore it? :)/*or*/or//can appear within a string literal in which case you do NOT want to remove them. e.g."This string has /* in it and should not be touched!"