Bug Tracker

Opened 12 years ago

Closed 11 years ago

#10868 closed feature (wontfix)

feature request: .preimage

Reported by: gibson042 Owned by:
Priority: undecided Milestone: None
Component: unfiled Version: 1.7.1
Keywords: Cc:
Blocked by: Blocking:

Description (last modified by Rick Waldron)

I'd like a method that reverses the normal direction of selectors, used to find elements for which a .find with given selector would return the context element(s).

Sample usage:

function childDelegate( $element, selClickTarget, strEvents, fnHandler ) {
  return $( $element ).on( strEvents, selClickTarget, function() {
    if ( $( this ).preimage( "> " + selClickTarget, $element ) ) {
      return fn.apply(this, arguments);

childDelegate( $dl, "dt ~ dd > a:first-child", "click", function( evt ) {
  alert( "child dd clicked" );

Proposed signature: .preimage( selector [, candidates] )

The one-argument version returns a jQuery object containing all elements from which the results of .find(selector) would include a member of the context set.

The two-argument version is a short-circuiting alias for .preimage( selector ).is( candidates ), returning a boolean indicating intersection between the full results and a candidate set.

Implementation would add helper functions on the Sizzle relative operators (e.g., $.each({'>': $.fn.parent, '+': $.fn.prev, '~': $.fn.prevAll}, function(operator,fn){ try{$.expr.relative[operator].preimage=fn;}catch(x){} });) and a relatively simple function to parse/chunk selectors and incrementally build up the result set by working backwards through them.

A link to a working demonstration will be posted shortly.

Change History (15)

comment:1 Changed 12 years ago by ajpiano

Keywords: 1.8-discuss added

If you could give us a few details about the usecase for such a function as well, we'd really appreciate it. Is this meant to be an internal improvement to Sizzle? A user-facing API? Thanks!

comment:2 Changed 12 years ago by gibson042

It'd be a documented external API, but might ultimately have the potential to shrink Sizzle and/or jQuery codebases through internal use. Mostly, I want it to provide intuitive event handling for potentially-nesting widgets (#6696; #10762; etc.). It'll be valuable if we ever decide to support .on(events, ">...", fn), and will let jQuery users simulate support for it now.

The closure provided by reverse lookups shouldn't add much code weight, and has the potential to enable a lot of currently-unpredictable creative applications.

comment:3 Changed 12 years ago by Rick Waldron

-1, Feature creep

comment:4 Changed 12 years ago by dmethvin

-1, I have no idea what this is, which makes me think I am against it.

comment:5 Changed 12 years ago by dmethvin

Status: newopen

comment:6 Changed 12 years ago by gibson042

Plugin implementing request: http://plugins.jquery.com/project/preimage

Working example: http://jsbin.com/usabam

Uncompressed, and including unit tests and functionality backporting to support jQuery 1.4+ instead of 1.6+, the plugin is 5.88 KiB. If brought into jQuery proper, access to local variables and functions would eliminate redundancy and result in no more than a 100-200 byte initial increase in jquery.min.js, decreased if .preimage can be used to optimize existing functionality.

comment:7 Changed 11 years ago by jzaefferer

Description: modified (diff)

-1, Too much special-case.

comment:8 Changed 11 years ago by jaubourg

-1, I'd like to see a plugin first in order to assess usefulness.

comment:9 Changed 11 years ago by dmethvin

Description: modified (diff)

-1, The code was lost in the Great Depluginization Purge; I'd still like to see it but if it's 100-200 bytes it doesn't seem like it would land. Of course, you worked miracles with the undefined patch so maybe I should wait to see it.

comment:10 Changed 11 years ago by mikesherov

Description: modified (diff)

-1, gets us further away from qSa, when we should be moving more towards it.

comment:11 Changed 11 years ago by Timmy Willison


comment:12 Changed 11 years ago by Rick Waldron

Description: modified (diff)

-1, Feature creep

comment:13 Changed 11 years ago by gibson042

I was pointed to http://lists.w3.org/Archives/Public/public-webapps/2011OctDec/1454.html by timmywil, and in light of the similarities between this feature request and Element.matches(selector, reference), I'd like to redirect this one towards jQuery.fn.is(selector, reference) (as noted by Lachlan in the message, there is a basic equivalence between the two methods except for ours missing the latter signature).

I still think preimage functionality is useful, and is probably a dependency anyway, but the description of this ticket is no longer completely accurate. Should it be updated, or replaced?

comment:14 Changed 11 years ago by gibson042

#11124 resolves the bulk of this ticket. The remainder is essentially blocked by #11109.

comment:15 Changed 11 years ago by dmethvin

Keywords: 1.8-discuss removed
Resolution: wontfix
Status: openclosed

Voted off the island.

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