how to use the isundefined function from the underscore library in typescript

To use the isUndefined function from the Underscore library in Typescript, first install the underscore package using npm.

npm install underscore
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After installation, you can import the isUndefined function from the underscore package in your Typescript code using the following import statement:

index.ts
import { isUndefined } from 'underscore';
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You can then use the isUndefined function to check if a value is undefined as follows:

index.ts
const someVariable = undefined;

if (isUndefined(someVariable)) {
  console.log('The variable is undefined.');
} else {
  console.log('The variable is defined.');
}
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In the above example, the isUndefined function is used to check if the someVariable is undefined. If the variable is undefined, the function returns true and the first console.log statement is executed. Otherwise, the second console.log statement is executed.