Can anyone explain why the watch callback is triggered upon browser reload or Angular route change even when the old value and new value are the same? Here's an example:
$scope.test = "blah";
$scope.watch("test", function(new, old){
console.log(new === old);
}
Every time you reload the page or change routes away and back to that controller, the console log will show true. I had to add a guard inside the callback to prevent unnecessary callbacks. Did I make a mistake somewhere?
If you take a look at the documentation page here, you can find information about when this particular event occurs. The timing may vary based on how your application is structured, but a simple comparison using === will indicate whether there has been a change or not (as recommended).
I want to express my gratitude towards Mathew Berg for providing the solution I needed. By referring to the documentation, I was able to find the answer.
Upon registering a watcher with the scope, the listener function is executed asynchronously (via $evalAsync) to set up the watcher. In some rare instances, this may not be ideal as the listener gets triggered even when the watchExpression's result remains unchanged. To identify and handle this particular scenario within the listener function, one can compare the newVal and oldVal. If these two values are exactly identical (===), it indicates that the listener was invoked solely during initialization.
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