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WWW-Mechanize-Chrome-DOMops-0.02
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/ WWW::Mechanize::Chrome::DOMops

NAME

WWW::Mechanize::Chrome::DOMops - Operations on the DOM loaded in Chrome

VERSION

Version 0.02

SYNOPSIS

This module provides a set of tools to operate on the DOM of the provided WWW::Mechanize::Chrome object. Currently, supported operations are:

  • find() : finds HTML elements

  • zap() : deletes HTML elements

The selection of the HTML elements in the DOM can be done in various ways:

  • by a CSS selector,

  • by tag,

  • by class.

  • by id,

  • by name.

There is more information about this in section "ELEMENT SELECTORS".

Here are some usage scenaria:

  use WWW::Mechanize::Chrome::DOMops qw/zap find VERBOSE_DOMops/;

  # increase verbosity: 0, 1, 2, 3
  $WWW::Mechanize::Chrome::VERBOSE_DOMops = 3;

  # First, create a mech object and load a URL on it
  # Note: you need google-chrome binary installed in your system!
  my $mechobj = WWW::Mechanize::Chrome->new();
  $mechobj->get('https://www.bbbbbbbbb.com');

  # find elements in the DOM, select by id, tag, name, or 
  # by a CSS selector.
  my $ret = find({
     'mech-obj' => $mechobj,
     # find elements whose class is in the provided
     # scalar class name or array of class names
     'element-class' => ['slanted-paragraph', 'class2', 'class3'],
     # *OR* their tag is this:
     'element-tag' => 'p',
     # *OR* their name is this:
     'element-name' => ['aname', 'name2'],
     # *OR* their id is this:
     'element-id' => ['id1', 'id2'],
     # just provide a CSS selector and get done with it already
     'element-cssselector' => 'a-css-selector',
     # specifies that we should use the union of the above sets
     # hence the *OR* in above comment
     '||' => 1,
     # this says to find all elements whose class
     # is such-and-such AND element tag is such-and-such
     # '&&' => 1 means to calculate the INTERSECTION of all
     # individual matches.
     
     # optionally run javascript code on all those elements matched
     'find-cb-on-matched' => [
       {
         'code' =><<'EOJS',
// the element to operate on is 'htmlElement'
console.log("operating on this element "+htmlElement.tagName);
// this is returned back in the results of find() under
// key "find-cb-on-matched"
return 1;
EOJS
         'name' => 'func1'
       }, {...}
     ],
     # optionally run javascript code on all those elements
     # matched AND THEIR CHILDREN too!
     'find-cb-on-matched-and-their-children' => [
       {
         'code' =><<'EOJS',
// the element to operate on is 'htmlElement'
console.log("operating on this element "+htmlElement.tagName);
// this is returned back in the results of find() under
// key "find-cb-on-matched" notice the complex data
return {"abc":"123",{"xyz":[1,2,3]}};
EOJS
         'name' => 'func2'
       }
     ],
     # optionally ask it to create a valid id for any HTML
     # element returned which does not have an id.
     # The text provided will be postfixed with a unique
     # incrementing counter value 
     'insert-id-if-none' => '_prefix_id',
     # or ask it to randomise that id a bit to avoid collisions
     'insert-id-if-none-random' => '_prefix_id',

     # optionally, also output the javascript code to a file for debugging
     'js-outfile' => 'output.js',
  });


  # Delete an element from the DOM
  $ret = zap({
     'mech-obj' => $mechobj,
     'element-id' => 'paragraph-123'
  });

  # Mass murder:
  $ret = zap({
     'mech-obj' => $mechobj,
     'element-tag' => ['div', 'span', 'p'],
     '||' => 1, # the union of all those matched with above criteria
  });

  # error handling
  if( $ret->{'status'} < 0 ){ die "error: ".$ret->{'message'} }
  # status of -3 indicates parameter errors,
  # -2 indicates that eval of javascript code inside the mech object
  # has failed (syntax errors perhaps, which could have been introduced
  # by user-specified callback
  # -1 indicates that javascript code executed correctly but
  # failed somewhere in its logic.

  print "Found " . $ret->{'status'} . " matches which are: "
  # ... results are in $ret->{'found'}->{'first-level'}
  # ... and also in $ret->{'found'}->{'all-levels'}
  # the latter contains a recursive list of those
  # found AND ALL their children

EXPORT

the sub to find element(s) in the DOM

find()

the sub to delete element(s) from the DOM

zap()

and the flag to denote verbosity (default is 0, no verbosity)

$WWW::Mechanize::Chrome::DOMops::VERBOSE_DOMops

SUBROUTINES/METHODS

find($params)

It finds HTML elements in the DOM currently loaded on the parameters-specified WWW::Mechanize::Chrome object. The parameters are:

  • mech-obj : supply a WWW::Mechanize::Chrome, required

  • insert-id-if-none : some HTML elements simply do not have an id (e.g. <p>). If any of these elements is matched, its tag and its id (empty string) will be returned. By specifying this parameter (as a string, e.g. _replacing_empty_ids) all such elements matched will have their id set to _replacing_empty_ids_X where X is an incrementing counter value starting from a random number. By running find() more than once on the same on the same DOM you are risking having the same ID. So provide a different prefix every time. Or use insert-id-if-none-random, see below.

  • insert-id-if-none-random : each time find() is called a new random base id will be created formed by the specified prefix (as with insert-id-if-none) plus a long random string plus the incrementing counter, as above. This is supposed to be better at avoiding collisions but it can not guarantee it. If you are setting rand()'s seed to the same number before you call find() then you are guaranteed to have collisions.

  • find-cb-on-matched : an array of user-specified javascript code to be run on each element matched in the order the elements are returned and in the order of the javascript code in the specified array. Each item of the array is a hash with keys code and name. The former contains the code to be run assuming that the html element to operate on is named htmlElement. The code must end with a return statement. Basically the code is the body of a function without the preamble (signature and function name etc.) and the postamble. Key name is just for making this process more descriptive and will be printed on log messages and returned back with the results. Here is an example:

        'find-cb-on-matched' : [
      {
	# this returns a complex data type
        'code' => 'console.log("found id "+htmlElement.id); return {"a":"1","b":"2"};'
        'name' => 'func1'
      },
      {
        'code' => 'console.log("second func: found id "+htmlElement.id); return 1;'
        'name' => 'func2'
      },
    ]

  • find-cb-on-matched-and-their-children : exactly the same as find-cb-on-matched but it operates on all those HTML elements matched and also all their children and children of children etc.

  • js-outfile : optionally save the javascript code (which is evaluated within the mech object) to a file.

  • element selectors are covered in section "ELEMENT SELECTORS".

JAVASCRIPT HELPERS

There is one javascript function available to all user-specified callbacks:

  • getAllChildren(anHtmlElement) : it returns back an array of HTML elements which are the children (at any depth) of the given anHtmlElement.

RETURN VALUE:

The returned value is a hashref with at least a status key which is greater or equal to zero in case of success and denotes the number of matched HTML elements. Or it is -3, -2 or -1 in case of errors:

-3 : there is an error with the parameters passed to this sub.
-2 : there is a syntax error with the javascript code to evaluate eval() inside the mech object. Most likely this syntax error is with user-specified callback code.
-1 : there is a logical error while running the javascript code. For example a division by zero etc. This can be both in the callback code as well as in the internal javascript code for edge cases not covered by tests. Please report these.

If status is not negative, then this is success and its value denotes the number of matched HTML elements. Which can be zero or more. In this case the returned hash contains this

"found" => {
  "first-level" => [
    {
      "tag" => "NAV",
      "id" => "nav-id-1"
    }
  ],
  "all-levels" => [
    {
      "tag" => "NAV",
      "id" => "nav-id-1"
    },
    {
      "id" => "li-id-2",
      "tag" => "LI"
    },
  ]
}

Key first-level contains those items matched directly while key all-levels contains those matched directly as well as those matched because they are descendents (direct or indirect) of each matched element.

Each item representing a matched HTML element has two fields: tag and id. Beware of missing id or use insert-id-if-none or insert-id-if-none-random to fill in the missing ids.

If find-cb-on-matched or find-cb-on-matched-and-their-children were specified, then the returned result contains this additional data:

"cb-results" => {
   "find-cb-on-matched" => [
     [
       {
         "name" => "func1",
         "result" => {
           "a" => 1,
           "b" => 2
         }
       }
     ],
     [
       {
         "result" => 1,
         "name" => "func2"
       }
     ]
   ],
   "find-cb-on-matched-and-their-children" => ...
 },

find-cb-on-matched and/or find-cb-on-matched-and-their-children will be present depending on whether corresponding value in the input parameters was specified or not. Each of these contain the return result for running the callback on each HTML element in the same order as returned under key found.

HTML elements allows for missing id. So field id can be empty unless caller set the insert-id-if-none input parameter which will create a unique id for each HTML element matched but with missing id. These changes will be saved in the DOM. When this parameter is specified, the returned HTML elements will be checked for duplicates because now all of them have an id field. Therefore, if you did not specify this parameter results may contain duplicate items and items with empty id field. If you did specify this parameter then some elements of the DOM (those matched by our selectors) will have their missing id created and saved in the DOM.

Another implication of using this parameter when running it twice or more with the same value is that you can get same ids. So, always supply a different value to this parameter if run more than once on the same DOM.

zap($params)

It removes HTML element(s) from the DOM currently loaded on the parameters-specified WWW::Mechanize::Chrome object. The params are exactly the same as with "find($params)" except that insert-id-if-none is ignored.

zap() is implemented as a find() with an additional callback for all elements matched in the first level (not their children) as:

'find-cb-on-matched' => {
  'code' => 'htmlElement.parentNode.removeChild(htmlElement); return 1;',
  'name' => '_thezapper'
 };

RETURN VALUE:

Return value is exactly the same as with "find($params)"

ELEMENT SELECTORS

Element selectors are how one selects HTML elements from the DOM. There are 5 ways to select HTML elements: by id, class, tag, name or via a CSS selector. Multiple selectors can be specified as well as multiple criteria in each selector (e.g. multiple class names in a element-class selector). The results from each selector are combined into a list of unique HTML elements (BEWARE of missing id fields) by means of UNION or INTERSECTION of the individual matches

These are the valid selectors:

  • element-class : find DOM elements matching this class name

  • element-tag : find DOM elements matching this element tag

  • element-id : find DOM element matching this element id

  • element-name : find DOM element matching this element name

  • element-cssselector : find DOM element matching this CSS selector

And one of these two must be used to combine the results into a final list

&& : Intersection. When set to 1 the result is the intersection of all individual results. Meaning that an element will make it to the final list if it was matched by every selector specified. This is the default.
|| : Union. When set to 1 the result is the union of all individual results. Meaning that an element will make it to the final list if it was matched by at least one of the selectors specified.

DEPENDENCIES

This module depends on WWW::Mechanize::Chrome which, in turn, depends on the google-chrome executable be installed on the host computer. See WWW::Mechanize::Chrome::Install on how to install the executable.

AUTHOR

Andreas Hadjiprocopis, <bliako at cpan.org>

BUGS

Please report any bugs or feature requests to bug-www-mechanize-chrome-domops at rt.cpan.org, or through the web interface at https://rt.cpan.org/NoAuth/ReportBug.html?Queue=WWW-Mechanize-Chrome-DOMops. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.

SUPPORT

You can find documentation for this module with the perldoc command.

perldoc WWW::Mechanize::Chrome::DOMops

You can also look for information at:

DEDICATIONS

Almaz

ACKNOWLEDGEMENTS

CORION for publishing WWW::Mechanize::Chrome and all its contributors.

LICENSE AND COPYRIGHT

Copyright 2019 Andreas Hadjiprocopis.

This program is free software; you can redistribute it and/or modify it under the terms of the the Artistic License (2.0). You may obtain a copy of the full license at:

http://www.perlfoundation.org/artistic_license_2_0

Any use, modification, and distribution of the Standard or Modified Versions is governed by this Artistic License. By using, modifying or distributing the Package, you accept this license. Do not use, modify, or distribute the Package, if you do not accept this license.

If your Modified Version has been derived from a Modified Version made by someone other than you, you are nevertheless required to ensure that your Modified Version complies with the requirements of this license.

This license does not grant you the right to use any trademark, service mark, tradename, or logo of the Copyright Holder.

This license includes the non-exclusive, worldwide, free-of-charge patent license to make, have made, use, offer to sell, sell, import and otherwise transfer the Package with respect to any patent claims licensable by the Copyright Holder that are necessarily infringed by the Package. If you institute patent litigation (including a cross-claim or counterclaim) against any party alleging that the Package constitutes direct or contributory patent infringement, then this Artistic License to you shall terminate on the date that such litigation is filed.

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