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#9477 closed bug (wontfix)
Opened June 01, 2011 06:46AM UTC
Closed June 13, 2011 09:31PM UTC
Last modified June 22, 2011 07:18AM UTC
extend (deep) merges arrays fields instead of replacing them
| Reported by: | tsvetomir | Owned by: | tsvetomir |
|---|---|---|---|
| Priority: | low | Milestone: | 1.next |
| Component: | core | Version: | 1.6.1 |
| Keywords: | neededdocs | Cc: | |
| Blocked by: | Blocking: |
Description
A deep extend does not overwrite array fields, but tries to merge them.
Example: [0, 1, 2] and ![3] produce [3, 1, 2] instead of ![3].
[
This behavior is not consistent or expected. If we apply it on strings "abc" and "d" should merge to "dbc".
Possibly related issue: [
Attachments (0)
Change History (13)
Changed June 01, 2011 03:14PM UTC by comment:1
| component: | unfiled → core |
|---|---|
| owner: | → rwaldron |
| status: | new → assigned |
Changed June 01, 2011 03:14PM UTC by comment:2
| owner: | rwaldron → tsvetomir |
|---|---|
| status: | assigned → pending |
Changed June 01, 2011 05:21PM UTC by comment:3
Yeah, this looks correct to me. Object and Array are extended, but primitive string/boolean/number are not.
Changed June 01, 2011 05:35PM UTC by comment:4
That's how I've always understood "extend" functions to behave, hopefully the OP will have references that will "enlighten" us.
Changed June 02, 2011 08:30AM UTC by comment:5
| status: | pending → new |
|---|
We have a defined behavior for extending objects (union), but we shouldn't assume that the user expects the same for sets of data.
Arrays should be treated as sets of data and not like objects. They can be combined in an union, intersection, a complement or in a user-defined way.
These two similar implementations yield the result I'd expect:
Object.extend (Prototype)
Object.append (Mootools)
Changed June 02, 2011 03:38PM UTC by comment:6
| priority: | undecided → low |
|---|---|
| resolution: | → worksforme |
| status: | new → closed |
This yields the results exactly as shown above: http://jsfiddle.net/rwaldron/zkCZt/
Changed June 02, 2011 07:25PM UTC by comment:7
extend(a, b) vs. extend(true, a, b)
You need to supply the true (deep) parameter to reproduce the issue. Otherwise you're overwriting the "nested" object http://jsfiddle.net/MN5xQ/
Changed June 02, 2011 07:50PM UTC by comment:8
p.s. Turns out Prototype and Mootools don't have a true deep extend. They always overwrite nested objects and arrays. Sorry for comparing apples to oranges!
Either way, I'm not the only one confused by this behavior.
See http://forum.jquery.com/topic/jquery-extend-modifies-but-not-replaces-array-properties-on-deep-copy
Changed June 13, 2011 10:14AM UTC by comment:9
I just ran into this.
See: http://jsfiddle.net/s5jNF/
I would expect Arrays to be overwritten or appended. But don't replace the individual elements piecemeal, which is what happens now.
Personally I need a deep extend where the array elements are appended. (Although I can see cases where I would want them overwritten.)
Can we get this as an option?
rwaldron, please reopen this. It's not worksforsome - it's wontfix or it's open.
Changed June 13, 2011 02:47PM UTC by comment:10
| resolution: | worksforme |
|---|---|
| status: | closed → reopened |
Changed June 13, 2011 08:49PM UTC by comment:11
Not sure why it can't be closed worksforme with needsdocs. The proposed changes might break existing code, which would be one reason to avoid changing it. For specific needs it is no doubt faster (performance-wise) to write a custom extend method, our poor method is already overburdened with constraints.
Changed June 13, 2011 09:31PM UTC by comment:12
| description: | A deep '''extend''' does not overwrite array fields, but tries to merge them. \ \ Example: [0, 1, 2] and ![3] produce [3, 1, 2] instead of ![3]. \ [http://jsfiddle.net/9xBw4/] \ \ This behavior is not consistent or expected. If we apply it on strings "abc" and "d" should merge to "dbc". \ \ Possibly related issue: [http://bugs.jquery.com/ticket/6958] → A deep '''extend''' does not overwrite array fields, but tries to merge them. \ \ Example: [0, 1, 2] and ![3] produce [3, 1, 2] instead of ![3]. \ [ \ \ This behavior is not consistent or expected. If we apply it on strings "abc" and "d" should merge to "dbc". \ \ Possibly related issue: [ |
|---|---|
| keywords: | → needsdocs |
| resolution: | → wontfix |
| status: | reopened → closed |
Changed June 22, 2011 07:18AM UTC by comment:13
| keywords: | needsdocs → neededdocs |
|---|
Updated: http://api.jquery.com/jQuery.extend/
Can you cite references of what you believe to be the correct behaviour?