I have difficulty understanding the following codes even with the comments
// Store the initial cell value so we can reset to it if need be
var oldCellValue;
var dereg = scope.$watch('ngModel', function() {
oldCellValue = ngModel.$modelValue;
dereg(); // only run this watch once, we don't want to overwrite our stored value when the input changes
});
How many time does function dereg got called in this case? Is this a recursion?
The code you've shown is in a nutshell
$watch() returned value (see below $rootScope.$watch returned value)$watch() called, it calls that referenced function - which leads to ubinding of that $watch()Read this nice article
a small extract from a summary:
As you can see, we're storing the function reference returned by the
$watch()statement; then, once the$watch()fires a few times, we invoke that stored method, unbinding the $watch() listener.
In that example, there is an if statement, which could help us to decide, when is the best time to remove that $watch() (e.g. after the first evaluation) ...
The more detailed defintion of the scope.$watch() could be found here:
And as we can see from this extract:
$watch(watchExpression, [listener], [objectEquality]);...
Returns a deregistration function for this listener.
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