angularjsHow do I use the $watch variable in AngularJS?

The $watch variable in AngularJS is used to watch for changes in a variable or an expression. It is a function that is called whenever the value of the expression changes.

For example, the following code block will watch for changes in the variable myVar and log the new value when it changes:

$scope.$watch('myVar', function(newValue, oldValue) {
  console.log(newValue);
});

The $watch function takes two parameters: the expression to watch and the callback function to be called when the value of the expression changes. The callback function takes two parameters: the new value and the old value of the expression.

The $watch function returns a deregistration function that can be used to unregister the watch. This is useful when the watch is no longer needed.

Here is an example of using the deregistration function:

var deregistrationFn = $scope.$watch('myVar', function(newValue, oldValue) {
  console.log(newValue);
});

// Later on when the watch is no longer needed
deregistrationFn();

Helpful links

• AngularJS $watch Documentation
• AngularJS $watch Tutorial

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