JavaScript

Backbone.js Collection pop() Method

This Backbone.js framework tutorial will discuss the pop() method in the collection class.

Introduction

Backbone.js is a framework that is used to build web applications that follow the style of JavaScript.

It supports models, events, collections, views, and utilities.

Using any of the previous functionalities, we can create and perform different operations on the given data in a web application.

Points to Remember

1. It is used with JavaScript.

2. We can implement the framework inside the <script> tag.

3. This framework supports JavaScript methods and functions like output and reading input.

4. <script> tag is placed inside <head> tag or in <body> tag.

5. It is important to have Content Delivery Network (CDN) links to run the web application on the server.

Let’s See the Structure To Place the Code

<html>

<head>

<script>

You can use Backbone.js framework here

</script>

</head>

<body>

<script>

You can also use Backbone.js framework here

</script>

</body>

</html>

CDN Links are placed with the src attribute of the script tag.

CDN Links

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.2/underscore-min.js" ></script>

<script src="https://cdnjs.cloudflare.com/ajax/libs/backbone.js/1.1.2/backbone-min.js" ></script>

The pop() method in Backbone.js collection removes the last instance of model from the collection.

Syntax:

collection_object.remove(options)

It takes one parameter.

The options parameter is to specify the model type.

Model – collection_object.pop()

Approach

1. Create a Backbone model using the extend() method.

Syntax:

var ModelClass = Backbone.Model.extend();

2. Create a Backbone collection using the extend() method and pass the model class.

Syntax:

var CollectionClass = Backbone.Collection.extend({

model: ModelClass

});

3. Create an object or instance for the collection class.

Syntax:

var collection_instance = new CollectionClass();

4. Explore the pop() method in the Backbone.js collection.

Let’s discuss several examples of the Backbone.js collection pop() method.

Example 1: Pop Last Instance Model From a Single Model to the Collection

In this example, we will create a Modal class named – Flowers and create a FlowerCollection collection class. We will pass our model class (Flowers) inside it.

After that, we have to create an instance for the Flowers model with three attributes(flower_name,flower_sepals,flower_petals).

We will create a flower_collection, which is an instance of the FlowerCollection collection. And we will add the instance of the Flower model to the collection instance using the add() method.

Now, we will remove this added model instance from the collection using the pop() method.

Finally, we are displaying the collection using the toJSON() method.

<html>

<head>

<script src="https://code.jquery.com/jquery-2.1.3.min.js" ></script>

 

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.2/underscore-min.js" ></script>

<script src="https://cdnjs.cloudflare.com/ajax/libs/backbone.js/1.1.2/backbone-min.js" ></script>

 

</head>

<body>

<center>

<h1>Linux Hint</h1>

</center>

<script>

 

//create Model named Flowers using extend()

var Flowers = Backbone.Model.extend();

 

//create collection - FlowerCollection and and pass Flowers model

var FlowerCollection = Backbone.Collection.extend({

model: Flowers

});

 

//create 1 instance for the Flowers model

var flower1 = new Flowers({flower_name: "lotus", flower_sepals:3,flower_petals:7});

//create flower_collection

var flower_collection = new FlowerCollection();

 

//add the above model instance to the flower_collection instance using add(() method.

flower_collection.add(flower1);

 

//display the flowers present in the collection

document.write('<strong> Flowers:</strong> ' + JSON.stringify(flower_collection.toJSON()));

 

document.write("<br>");

 

//remove flower1 from collection

flower_collection.pop(flower1);

 

//display the flowers present in the collection

document.write('<strong>After popping flower1 from Flowers:</strong> ' + JSON.stringify(flower_collection.toJSON()));

 

 

</script>

</body>

</html>

Output:

Run the application in your browser by saving the code in the file with .html as an extension.

Here, the pop() method removes the last instance from the collection.

Example 2: Pop Last Instance Model From Array of Models to the Collection

In this example, we will create a Modal class named – Flowers and create a FlowerCollection collection class. We will pass our model class (Flowers) inside it.

After that we have to create an instance for the Flowers model with three attributes(flower_name,flower_sepals,flower_petals).

We will create a flower_collection which is an instance of the FlowerCollection collection. And we will add three instances of the Flower model to the collection instance using the add() method.

Now, we will remove the last added model instance using the pop() method.

Finally, we are displaying the collection using the toJSON() method.

<html>

<head>

<script src="https://code.jquery.com/jquery-2.1.3.min.js" ></script>

 

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.2/underscore-min.js" ></script>

<script src="https://cdnjs.cloudflare.com/ajax/libs/backbone.js/1.1.2/backbone-min.js" ></script>

 

</head>

<body>

<center>

<h1>Linux Hint</h1>

</center>

<script>

 

//create Model named Flowers using extend()

var Flowers = Backbone.Model.extend();

 

//create collection - FlowerCollection and and pass Flowers model

var FlowerCollection = Backbone.Collection.extend({

model: Flowers

});

 

//create 3 instances for the Flowers model

var flower1 = new Flowers({flower_name: "lotus", flower_sepals:3,flower_petals:7});

var flower2 = new Flowers({flower_name: "lilly", flower_sepals:10,flower_petals:17});

var flower3 = new Flowers({flower_name: "rose", flower_sepals:3,flower_petals:1});

 

 

//create flower_collection

var flower_collection = new FlowerCollection();

 

//add the above model instances to the flower_collection instance using add(() method.

flower_collection.add([flower1,flower2,flower3]);

 

//display the flowers present in the collection

document.write('<strong>Existing:</strong> ' + JSON.stringify(flower_collection.toJSON()));

 

document.write("<br>");

 

//remove flower3

flower_collection.pop();

 

//display the flowers present in the collection

document.write('<strong>After popping flower3 from Flowers:</strong> ' + JSON.stringify(flower_collection.toJSON()));

 

document.write("<br>");

</script>

</body>

</html>

 

Output:

Run the application in your browser by saving the code in the file with .html as an extension.

Here, we can see the pop() method removes flower3 from the collection, and the remaining instances, flower1 and flower2, are displayed.

Conclusion

In this Backbone.js tutorial, we discussed the pop() method in collection. It is used to remove the last instance model from the collection. It is similar to the remove() method, but it won’t take any model instance as a parameter. It simply removes the last instance model.

About the author

Gottumukkala Sravan Kumar

B tech-hon's in Information Technology; Known programming languages - Python, R , PHP MySQL; Published 500+ articles on computer science domain