Peek-A-Bug

Peek into a minified source code to find a bug.

Ever tried to debug JavaScript code in production and all you get is a reference to an ambiguous line of minified file with a high number column location? Then you try to reproduce the problem in development mode and it never happens again? Eventually give up and download the minified source code and try to decipher the column location and context in question?

Well I used to do that in order to find the most cryptical of errors that happened in rare circumstances. I eventually got tired of it and created this little command line tool that automatically fetches the file, looks up the row and column, deciphers the current context and prettifies the scope to produce a human readable block of code.

How to install

Requirements: NodeJS

npm install peekabug -g

Running

peekabug [options] <url>[:row[:col]]

Where the url can be either a local file path or a web URI.

Options

-h, --help                output usage information
-V, --version             output the version number
-C, --chars <num>         define how many characters to include around the specified target
-r, --row <num>           define the row to look for
-c, --column --col <num>  define the character column to search for
-d, --depth <num>         define the depth
-x, --cursor <row:col>    define cursor position to seek for
-u, --uglify              no beautify for the output

Examples

peekabug http://ajax.googleapis.com/ajax/libs/jquery/1.5.1/jquery.min.js:16:1545

Output:

{
    c || bq.test(a) ? e(a, f) : bO(a + "[" + (typeof f === "object" || d.isArray(f) ? b : "") + "]", f, c, e)
}

You can expand the search area by defining the depth to seek:

peekabug --depth 2 http://ajax.googleapis.com/ajax/libs/jquery/1.5.1/jquery.min.js:16:1545

or

peekabug --depth 2 --cursor 16:1545 http://ajax.googleapis.com/ajax/libs/jquery/1.5.1/jquery.min.js

Output:

{
    if (d.isArray(b) && b.length) d.each(b, function(b, f) {
        c || bq.test(a) ? e(a, f) : bO(a + "[" + (typeof f === "object" || d.isArray(f) ? b : "") + "]", f, c, e)
    });
    else if (c || b == null || typeof b !== "object") e(a, b);
    else if (d.isArray(b) || d.isEmptyObject(b)) e(a, "");
    else
        for (var f in b) bO(a + "[" + f + "]", b[f], c, e)
}

From a local file:

peekabug vendor/jquery.min.js:16:1545

Output:

{
    c || bq.test(a) ? e(a, f) : bO(a + "[" + (typeof f === "object" || d.isArray(f) ? b : "") + "]", f, c, e)
}

Prefer to output the code non-minified? No problem:

peekabug --uglify vendor/jquery.min.js:16:1545

Output:

{c||bq.test(a)?e(a,f):bO(a+"["+(typeof f==="object"||d.isArray(f)?b:"")+"]",f,c,e)}

Author

Jyrki Laurila

License (MIT)

WWWWWW||WWWWWW
 W W W||W W W
      ||
    ( OO )__________
     /  |           \
    /o o|    MIT     \
    \___/||_||__||_|| *
         || ||  || ||
        _||_|| _||_||
       (__|__|(__|__|

Copyright © 2014 Jyrki Laurila

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.