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

To use the reject function from the Underscore library in Typescript, you need to first install the Underscore library and its types as dependencies. You can do this by running the following commands:

npm install underscore
npm install @types/underscore
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Once you have installed the Underscore library and its types, you can use the reject function in your Typescript code as follows:

index.ts
import * as _ from 'underscore';

interface Person {
  name: string;
  age: number;
}

const people: Person[] = [
  { name: 'Alice', age: 25 },
  { name: 'Bob', age: 30 },
  { name: 'Charlie', age: 35 }
];

const rejectedPeople = _.reject(people, person => person.age > 30);

console.log(rejectedPeople);
// Output: [{ name: 'Alice', age: 25 }, { name: 'Bob', age: 30 }]
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In the above example, we have defined an interface Person which has name and age properties. We have created an array of Person objects, and used the reject function to remove any Person object whose age property is greater than 30. We have then logged the resulting array of Person objects to the console.

Note that we have imported the Underscore library using the wildcard syntax, import * as _ from 'underscore';. This imports all of the functions from the Underscore library into the _ object, which we can then use to access the reject function.

Also note that we have used an arrow function as the second argument to the reject function. This is because Typescript does not automatically provide type definitions for functions from external libraries. However, the types for the Underscore library are provided by the @types/underscore package, which we installed earlier. This allows us to use the Person interface as the type of the argument to the arrow function.