A query parameter is part of the URL that allows additional parameters to be passed into a path. For example, /search?criteria=typescript has a query parameter called criteria with a value of typescript.

In this section, we are going to implement a query parameter on the search page called criteria, which will drive the search. We'll implement the search page along the way. Let's carry out these steps to do this:

1. We are going to start in QuestionsData.ts by creating a function to simulate a search via a web request:

export const searchQuestions = async (
  criteria: string,
): Promise<QuestionData[]> => {
  await wait(500);
  return questions.filter(
    q =>
      q.title.toLowerCase().indexOf(criteria.toLowerCase()) >=
        0 ||
      q.content.toLowerCase().indexOf(criteria.toLowerCase()) >=
        0,
  );
};

So, the function uses...