How does AngularJS manage scope in ng-repeats?

Question

I have a table that has around 60 rows and 20 columns.  Each cell has a directive with an isolated scope.  I use 2 nested ng-repeats to generate the table (one for rows and one for columns), but I'm wondering how angular handles scope when a digest cycle causes a re-generation of the directives in the ng-repeats?

Does it destroy all the previous isolated scopes in my directives and create new ones, or are those old isolated scopes now orphaned somewhere and memory leaking as more and more digests take place?

Is this something that I, as a developer, should be aware of and make sure to handle the destruction of any isolated scopes?

Paul Sweatte · Answer

Use the changelog and the test specs for a high-level understanding of ng-repeat and how it changed between Angular versions:

select: keep ngModel when selected option is recreated by ngRepeat
ngRepeat: add support to iterate an object's properties even if it does not inherit from Object
ngRepeat: do not sort object keys alphabetically
ngRepeat: allow extra whitespaces in (key,value) part of micro-syntax
ngRepeat: support cyclic object references in error messages
ngRepeat: preserve original position of elements that are being animated away
ngRepeat: improve errors for duplicate items
allow aliasAs identifiers which contain but do not match reserved words
make allowed aliasAs expressions more strict
simplify code and remove duplicate array.length access
optimize marking of nodes that are being removed via an animation
use no-proto objects for blockMaps
move work to compile fn
move updateScope fn to factory and reuse it for all repeaters
clone boundary comment nodes
ngRepeat: provide support for aliasing filtered repeater results as a scope member
ngRepeat: ensure that the correct (transcluded) scope is used
ngRepeat: allow for more flexible coding style in ngRepeat expression
ngRepeat: allow multiline expressions
ngRepeat: support repeating over ngInclude and other directives that replace repeated nodes
ngRepeat: correctly track elements even when the collection is initially undefined
ngRepeat: add $even and $odd props to iterator
handle iteration over identical obj values
support growing over multi-element groups
correctly iterate over array-like objects
prevent initial duplicates
ngRepeat: add support for custom tracking of items
ngRepeat: due to 61f2767c, it is now considered an error to have two identical items (identified by the new "track by" expression) in a collection that is fed into the repeater. This behavior was previously tolerated.
ngRepeat: correctly apply $last if repeating over object
ngRepeat: now works better with primitive types 
ngRepeat: expose $first, $middle and $last instead of $position

How does AngularJS manage scope in ng-repeats?

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