JavaScript implementation of Gzip

Question

I m writing a Web application that needs to store JSON data in a small  fixed-size server-side cache via AJAX  think  Opensocial quotas   I do not have control over the server   I need to reduce the size of the stored data to stay within a server-side quota  and was hoping to be able to gzip the stringified JSON in the browser before sending it up to the server   However  I cannot find much in the way of JavaScript implementations of Gzip  Any suggestions for how I can compress the data on the client side before sending it up

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I ported an implementation of LZMA from a GWT module into standalone JavaScript   It s called LZMA-JS

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I did not test  but there s a javascript implementation of ZIP  called JSZip  https   stuk github io jszip

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You can use a 1 pixel per 1 pixel Java applet embedded in the page and use that for compression   It s not JavaScript and the clients will need a Java runtime but it will do what you need

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I guess a generic client-side JavaScript compression implementation would be a very expensive operation in terms of processing time as opposed to transfer time of a few more HTTP packets with uncompressed payload   Have you done any testing that would give you an idea how much time there is to save  I mean  bandwidth savings can t be what you re after  or can it

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Most browsers can decompress gzip on the fly  That might be a better option than a javascript implementation

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Here are some other compression algorithms implemented in Javascript    Huffman LZ77

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I had another problem  I did not want to encode data in gzip but to decode gzipped data   I am running javascript code outside of the browser so I need to decode it using pure javascript   It took me some time but i found that in the JSXGraph library there is a way to read gzipped data   Here is where I found the library  http   jsxgraph uni-bayreuth de wp 2009 09 29 jsxcompressor-zlib-compressed-javascript-code  There is even a standalone utility that can do that  JSXCompressor  and the code is LGPL licencied   Just include the jsxcompressor js file in your project and then you will be able to read a base 64 encoded gzipped data    lt  doctype html gt   lt  head gt   lt title gt Test gzip decompression page lt  title gt   lt script src  jsxcompressor js  gt  lt  script gt   lt  head gt   lt body gt   lt script gt      document write JXG decompress   lt  php          echo base64 encode gzencode  Try not  Do  or do not  There is no try             gt       lt  script gt   lt  html gt    I understand it is not what you wanted but I still reply here because I suspect it will help some people

User · Answer

You can use a 1 pixel per 1 pixel Java applet embedded in the page and use that for compression   It s not JavaScript and the clients will need a Java runtime but it will do what you need

User · Answer

Most browsers can decompress gzip on the fly  That might be a better option than a javascript implementation

User · Answer

I guess a generic client-side JavaScript compression implementation would be a very expensive operation in terms of processing time as opposed to transfer time of a few more HTTP packets with uncompressed payload   Have you done any testing that would give you an idea how much time there is to save  I mean  bandwidth savings can t be what you re after  or can it

User · Answer

Most browsers can decompress gzip on the fly  That might be a better option than a javascript implementation

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Edit There appears to be a better LZW solution that handles Unicode strings correctly at http   pieroxy net blog pages lz-string index html  Thanks to pieroxy in the comments      I don t know of any gzip implementations  but the jsolait library  the site seems to have gone away  has functions for LZW compression decompression  The code is covered under the LGPL      LZW-compress a string function lzw encode s        var dict           var data    s       split          var out           var currChar      var phrase   data 0       var code   256      for  var i 1  i lt data length  i              currChar data i           if  dict phrase   currChar     null                phrase    currChar                    else               out push phrase length  gt  1   dict phrase    phrase charCodeAt 0                dict phrase   currChar    code              code                phrase currChar                      out push phrase length  gt  1   dict phrase    phrase charCodeAt 0        for  var i 0  i lt out length  i              out i    String fromCharCode out i              return out join            Decompress an LZW-encoded string function lzw decode s        var dict           var data    s       split          var currChar   data 0       var oldPhrase   currChar      var out    currChar       var code   256      var phrase      for  var i 1  i lt data length  i              var currCode   data i  charCodeAt 0           if  currCode  lt  256                phrase   data i                     else              phrase   dict currCode    dict currCode     oldPhrase   currChar                     out push phrase           currChar   phrase charAt 0           dict code    oldPhrase   currChar          code            oldPhrase   phrase            return out join

User · Answer

You can use a 1 pixel per 1 pixel Java applet embedded in the page and use that for compression   It s not JavaScript and the clients will need a Java runtime but it will do what you need

User · Answer

I guess a generic client-side JavaScript compression implementation would be a very expensive operation in terms of processing time as opposed to transfer time of a few more HTTP packets with uncompressed payload   Have you done any testing that would give you an idea how much time there is to save  I mean  bandwidth savings can t be what you re after  or can it

User · Answer

You can use a 1 pixel per 1 pixel Java applet embedded in the page and use that for compression   It s not JavaScript and the clients will need a Java runtime but it will do what you need

User · Answer

Edit There appears to be a better LZW solution that handles Unicode strings correctly at http   pieroxy net blog pages lz-string index html  Thanks to pieroxy in the comments      I don t know of any gzip implementations  but the jsolait library  the site seems to have gone away  has functions for LZW compression decompression  The code is covered under the LGPL      LZW-compress a string function lzw encode s        var dict           var data    s       split          var out           var currChar      var phrase   data 0       var code   256      for  var i 1  i lt data length  i              currChar data i           if  dict phrase   currChar     null                phrase    currChar                    else               out push phrase length  gt  1   dict phrase    phrase charCodeAt 0                dict phrase   currChar    code              code                phrase currChar                      out push phrase length  gt  1   dict phrase    phrase charCodeAt 0        for  var i 0  i lt out length  i              out i    String fromCharCode out i              return out join            Decompress an LZW-encoded string function lzw decode s        var dict           var data    s       split          var currChar   data 0       var oldPhrase   currChar      var out    currChar       var code   256      var phrase      for  var i 1  i lt data length  i              var currCode   data i  charCodeAt 0           if  currCode  lt  256                phrase   data i                     else              phrase   dict currCode    dict currCode     oldPhrase   currChar                     out push phrase           currChar   phrase charAt 0           dict code    oldPhrase   currChar          code            oldPhrase   phrase            return out join

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We just released pako https   github com nodeca pako   port of zlib to javascript  I think that s now the fastest js implementation of deflate   inflate   gzip   ungzip  Also  it has democratic MIT licence  Pako supports all zlib options and it s results are binary equal   Example   var inflate   require  pako lib inflate   inflate   var text   inflate zipped   to   string

User · Answer

Most browsers can decompress gzip on the fly  That might be a better option than a javascript implementation

User · Answer

Edit There appears to be a better LZW solution that handles Unicode strings correctly at http   pieroxy net blog pages lz-string index html  Thanks to pieroxy in the comments      I don t know of any gzip implementations  but the jsolait library  the site seems to have gone away  has functions for LZW compression decompression  The code is covered under the LGPL      LZW-compress a string function lzw encode s        var dict           var data    s       split          var out           var currChar      var phrase   data 0       var code   256      for  var i 1  i lt data length  i              currChar data i           if  dict phrase   currChar     null                phrase    currChar                    else               out push phrase length  gt  1   dict phrase    phrase charCodeAt 0                dict phrase   currChar    code              code                phrase currChar                      out push phrase length  gt  1   dict phrase    phrase charCodeAt 0        for  var i 0  i lt out length  i              out i    String fromCharCode out i              return out join            Decompress an LZW-encoded string function lzw decode s        var dict           var data    s       split          var currChar   data 0       var oldPhrase   currChar      var out    currChar       var code   256      var phrase      for  var i 1  i lt data length  i              var currCode   data i  charCodeAt 0           if  currCode  lt  256                phrase   data i                     else              phrase   dict currCode    dict currCode     oldPhrase   currChar                     out push phrase           currChar   phrase charAt 0           dict code    oldPhrase   currChar          code            oldPhrase   phrase            return out join

User · Answer

I guess a generic client-side JavaScript compression implementation would be a very expensive operation in terms of processing time as opposed to transfer time of a few more HTTP packets with uncompressed payload   Have you done any testing that would give you an idea how much time there is to save  I mean  bandwidth savings can t be what you re after  or can it

User · Answer

I did not test  but there s a javascript implementation of ZIP  called JSZip  https   stuk github io jszip

User · Answer

We just released pako https   github com nodeca pako   port of zlib to javascript  I think that s now the fastest js implementation of deflate   inflate   gzip   ungzip  Also  it has democratic MIT licence  Pako supports all zlib options and it s results are binary equal   Example   var inflate   require  pako lib inflate   inflate   var text   inflate zipped   to   string

User · Answer

Here are some other compression algorithms implemented in Javascript    Huffman LZ77

User · Answer

Edit There appears to be a better LZW solution that handles Unicode strings correctly at http   pieroxy net blog pages lz-string index html  Thanks to pieroxy in the comments      I don t know of any gzip implementations  but the jsolait library  the site seems to have gone away  has functions for LZW compression decompression  The code is covered under the LGPL      LZW-compress a string function lzw encode s        var dict           var data    s       split          var out           var currChar      var phrase   data 0       var code   256      for  var i 1  i lt data length  i              currChar data i           if  dict phrase   currChar     null                phrase    currChar                    else               out push phrase length  gt  1   dict phrase    phrase charCodeAt 0                dict phrase   currChar    code              code                phrase currChar                      out push phrase length  gt  1   dict phrase    phrase charCodeAt 0        for  var i 0  i lt out length  i              out i    String fromCharCode out i              return out join            Decompress an LZW-encoded string function lzw decode s        var dict           var data    s       split          var currChar   data 0       var oldPhrase   currChar      var out    currChar       var code   256      var phrase      for  var i 1  i lt data length  i              var currCode   data i  charCodeAt 0           if  currCode  lt  256                phrase   data i                     else              phrase   dict currCode    dict currCode     oldPhrase   currChar                     out push phrase           currChar   phrase charAt 0           dict code    oldPhrase   currChar          code            oldPhrase   phrase            return out join

User · Answer

I ported an implementation of LZMA from a GWT module into standalone JavaScript   It s called LZMA-JS

User · Answer

I had another problem  I did not want to encode data in gzip but to decode gzipped data   I am running javascript code outside of the browser so I need to decode it using pure javascript   It took me some time but i found that in the JSXGraph library there is a way to read gzipped data   Here is where I found the library  http   jsxgraph uni-bayreuth de wp 2009 09 29 jsxcompressor-zlib-compressed-javascript-code  There is even a standalone utility that can do that  JSXCompressor  and the code is LGPL licencied   Just include the jsxcompressor js file in your project and then you will be able to read a base 64 encoded gzipped data    lt  doctype html gt   lt  head gt   lt title gt Test gzip decompression page lt  title gt   lt script src  jsxcompressor js  gt  lt  script gt   lt  head gt   lt body gt   lt script gt      document write JXG decompress   lt  php          echo base64 encode gzencode  Try not  Do  or do not  There is no try             gt       lt  script gt   lt  html gt    I understand it is not what you wanted but I still reply here because I suspect it will help some people

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