Deprecation Guide for Function.prototype.observes

Historically, Ember has extended the Function.prototype with a few functions (on, observes, property), over time we have moved away from using these prototype extended functions in favor of using the official ES modules based API.

In order to migrate away from Function.prototype.observes you would update to using observer from @ember/object (see documentation) directly.

For example, you would migrate from:

import EmberObject from '@ember/object';

export default EmberObject.extend({
  valueObserver: function() {
    // Executes whenever the "value" property changes
  }.observes('value')
});

Into:

import EmberObject, { observer } from '@ember/object';

export default EmberObject.extend({
  valueObserver: observer('value', function() {
    // Executes whenever the "value" property changes
  })
});

Please review the deprecation RFC over at emberjs/rfcs for more details.