What is a prototype pattern?

The prototype pattern is one of the Creational pattern groups. The responsibility is to create a new object through clone the existing object instead of using the new key. The new object is the same as the original object, and we can change its property does not impact the original object.

When should I use the prototype pattern?

The singleton pattern should be used when a developer wants to:

• Initialize an object that is the same as the original object without using a new operator or constructor because we could be missing some properties of the original object leading to the new key does not use.
• Initialize object at run-time.
• The properties to init an object is complex.

How to implement

For example, we will define a class that has the responsibility to generate a CSV file with a header and name.

export class ExportCsvFile {
  public _name: string;
  public _headers: string[] = ['#', 'Username', 'Email'];
  
  constructor(name: string, headers: string[]) {
    this._name = name;
    this._headers = [...this._headers, ...headers];
  }


  public clone(): this {
    return Object.create(this);
  }
}

const csvFile1 = new ExportCsvFile('CSV 1', []);
console.log(csvFile1._name);
console.log(csvFile1._headers);


const csvFile2 = csvFile1.clone();
csvFile2._name = 'CSV 2'
csvFile2._headers = [...csvFile2._headers, 'Is Activate', 'Last Login'];
console.log(csvFile2._name);
console.log(csvFile2._headers);

Execution result

CSV 1

[ '#', 'Username', 'Email' ]

CSV 2

[ '#', 'Username', 'Email', 'Is Activate', 'Last Login' ]

Pros and Cons

Pros:

• You can clone objects without coupling to their concrete classes.
• You can get rid of repeated initialization code in favor of cloning pre-built prototypes.
• You can produce complex objects more conveniently.
• You get an alternative to inheritance when dealing with configuration presets for complex objects.

Cons:

• Cloning complex objects that have circular references might be very tricky.

Wrapping Up

Thank you for reading, and happy coding!

I hope this article will help make the concepts of the Prototype Pattern