In this article, we will see the Backbone.js hasChanged() model. The hasChanged() model checks if the model is changed or not, i.e. it will return a boolean value as true if the value is changed, otherwise returns a false value, since its last set, in order to set that value for an attribute in the model.
Syntax:
Backbone.Model.hasChanged(attribute);
Parameter Value:
- attribute: This parameter specifies the property of the model.
Example 1: In this example, we will update the value of a model and check using the hasChanged() model.
HTML
<!DOCTYPE html> <html> <head> type="text/javascript"> </script> <script src= type="text/javascript"> </script> <script src= type="text/javascript"> </script> </head> <body> <script type="text/javascript"> var Books = Backbone.Model.extend(); var book = new Books({ book_name: "css" }); document.write('Actual Values: ' + JSON.stringify(book)); document.write("<br>"); document.write('Actual Value Changed ?: ' + book.hasChanged()); book.set('book_name', 'php'); document.write("<br>"); document.write("<br>"); document.write('Changed Values: ' + JSON.stringify(book)); document.write("<br>"); document.write('Actual Value Changed ?: ' + book.hasChanged()); </script> </body> </html> |
Output:
Actual Values: {"book_name":"css"}
Actual Value Changed ?: false
Changed Values: {"book_name":"php"}
Actual Value Changed ?: true
Example 2: In this example, we will update the value of an empty model and check using the hasChanged() model.
HTML
<!DOCTYPE html> <html> <head> type="text/javascript"> </script> <script src= type="text/javascript"> </script> <script src= type="text/javascript"> </script> </head> <body> <script type="text/javascript"> var Books = Backbone.Model.extend(); var book = new Books({}); document.write('Actual Values: ' + JSON.stringify(book)); document.write("<br>"); document.write('Actual Value Changed ?: ' + book.hasChanged()); book.set('book_name', 'php'); document.write("<br>"); document.write("<br>"); document.write('Changed Values: ' + JSON.stringify(book)); document.write("<br>"); document.write('Actual Value Changed ?: ' + book.hasChanged()); </script> </body> </html> |
Output:
Actual Values: {}
Actual Value Changed ?: false
Changed Values: {"book_name":"php"}
Actual Value Changed ?: true
Reference: https://backbonejs.org/#Model-hasChanged
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