Here's an example of a prompt we could use:

using js in the inspector, calculate a web page's flesch-kincaid grade level score

In ChatGPT, this returned the following, which could be saved as a Snippet and run on any page:

// Function to calculate the Flesch-Kincaid Grade Level score
function calculateFleschKincaid(text) {
  // Split the text into sentences
  const sentences = text.match(/[^.!?]+[.!?]+/g) || [];
  
  let totalWords = 0;
  let totalSyllables = 0;

  // Calculate the total number of words and syllables
  sentences.forEach((sentence) => {
    const words = sentence.split(/\s+/);
    totalWords += words.length;

    words.forEach((word) => {
      totalSyllables += countSyllables(word);
    });
  });

  // Calculate the Flesch-Kincaid Grade Level score
  const averageWordsPerSentence = totalWords / sentences.length;
  const averageSyllablesPerWord = totalSyllables / totalWords;

  const score =
    0.39 * averageWordsPerSentence +
    11.8 * averageSyllablesPerWord -
    15.59;

  return score.toFixed(2);
}

// Function to count syllables in a word
function countSyllables(word) {
  word = word.toLowerCase().replace(/[^a-z]/g, '');
  if (word.length <= 3) return 1;
  word = word.replace(/(?:[^laeiouy]es|ed|[^laeiouy]e)$/g, '');
  word = word.replace(/^y/, '');
  return (word.match(/[aeiouy]{1,2}/g) || []).length;
}

// Get the text content of the web page
const textContent = document.body.textContent || '';

// Calculate the Flesch-Kincaid Grade Level score and log it to the console
const score = calculateFleschKincaid(textContent);
console.log(`Flesch-Kincaid Grade Level Score: ${score}`);