Use of $watch and $observe

$observe is a method of the attribute object that listens for changes in the property values in the DOM. For example attr1= "{{name}}"

attribute is defined on the third parameter of the link function in directive. So $observe can only be used in directive.

You can see that its callback function has only one parameter, which is the new value.

    function () {        return  {            function(scope, element, attrs) {                attrs. $observe (  function(newval) {                    //....                 })            }        }    })

Summarized as follows:

$observe can only be used in directive, $watch not so many restrictions, $watch is the method on the scope object, so it can be used in the Controller or directive link method.

$observe can only be monitored for changes in DOM property values, $watch can listen to an expression, which can be a function or a string. If it is a string, it is converted to a function using $parse. String expression cannot contain {{}}.

$observe callback functions are newvalue, $watch have oldvalue and newvalue

Use of $watch and $observe