Create Extension Method in typescript - String.IsNullOrEmpty()

How to Create Extension Method using Typescript in Angular Application - String.IsNullOrEmpty()

Step 1 : Create typings.d.ts (declaration file) in the application and declare the method in interface like below.

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interface StringConstructor {
    isNullOrEmpty(value: string): boolean;
}

Step 2 : Create extension.ts file in the application and implement the method like below.

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String.isNullOrEmpty = function (value: string): boolean {
  return value === undefined || value.trim() === '' || value === null;
};

Step 3 : Usage of the Method in the component or class file.

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import './extensions';

export class TestComponent implements OnInit {

  public ngOnInit(): void {

  let abc;

  console.log(String.isNullOrEmpty(abc));

  }

}

Step 4 : Output like below.