backbone.jsHow can I use the "onchange" event in Backbone.js?

The onchange event can be used in Backbone.js to detect when a model's attribute has been changed. It is triggered when a set or change event is fired on the model.

For example, if a model had an attribute name and it was changed, the onchange event would be triggered:

var Model = Backbone.Model.extend({
  initialize: function() {
    this.on('change', function() {
      console.log('Name changed!');
    });
  }
});

var model = new Model({ name: 'John' });
model.set('name', 'Bob');

// Output: 'Name changed!'

The onchange event can also take a callback function as an argument:

var Model = Backbone.Model.extend({
  initialize: function() {
    this.on('change', function(model) {
      console.log('Name changed to ' + model.get('name'));
    });
  }
});

var model = new Model({ name: 'John' });
model.set('name', 'Bob');

// Output: 'Name changed to Bob'

The callback function will be passed the model as an argument, which can be used to get the changed attribute's new value.

The onchange event is part of the Backbone.Events API, which provides methods for binding and triggering custom events on a Backbone object.

Helpful links

• Backbone.Events API
• Backbone.Model.set()
• Backbone.Model.change()

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