Backbone.js hasChanged Model
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
Last Updated :
20 Jun, 2022
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