如何使这些数组正常运行？

Question

my +getRndFromArray are not grabbing from the correct array and are instead choosing any option from the arrays in the "what genre do you prefer from the following?" questions. The arrays for this are at the start of the code (not shown in the snippet) and I have a

function getRndFromArray(arrayName){                                
return arrayName[Math.floor(Math.random()*arrayName.length)]; 
}   

after the arrays at the start of the code

do {
  var strng = prompt(
    "Do you prefer fiction or non fiction books? From here I can choose a genre of book for you to read"
  );
  var fiction = strng.includes("fiction");
  var nonfiction = strng.includes("non fiction");

  if (fiction == true) {
    var strng = prompt(
      "What genre do you prefer from the following? Fantasy, Science Fiction, Romance, Action, Mystery"
    );
    var fantasy = strng.includes("Fantasy");
    var sciencefiction = strng.includes("Science Fiction");
    var romance = strng.includes("Romance");
    var action = strng.includes("Action");
    var mystery = strng.includes("Mystery");
    if (fantasy == true) {
      alert("I think you will enjoy " +getRndFromArray(FantasyArray));
    } else if (sciencefiction == true) {
      alert("I think you will enjoy " +getRndFromArray(ScienceFictionArray));
    } else if (romance == true) {
      alert("I think you will enjoy " +getRndFromArray(RomanceArray));
    } else if (action == true) {
      alert("I think you will enjoy " +getRndFromArray(ActionArray));
    } else mystery == true;
    {
      alert("I think you will enjoy " +getRndFromArray(MysteryArray));
    }
  }

  if (nonfiction == true) {
    var strng = prompt(
      "What genre do you prefer from the following? Self Help, Cooking, Health, Business"
    );
    var selfhelp = strng.includes("Self Help");
    var cooking = strng.includes("Cooking");
    var health = strng.includes("Health");
    var business = strng.includes("Business");
    if (selfhelp == true) {
      alert("I think you will enjoy " +getRndFromArray(SelfHelpArray));
    } else if (cooking == true) {
      alert("I think you will enjoy " +getRndFromArray(CookingArray));
    } else if (health == true) {
      alert("I think you will enjoy " +getRndFromArray(HealthArray));
    } else if (business == true) {
      alert("I think you will enjoy " +getRndFromArray(BusinessArray));
    } //if no option is inputed this set of code will run
    else {
      var again = prompt(
        "You have not told me whether you prefer fiction or non fiction. Would you like to try again? Yes or No?"
      );
    }
  } // prompt relating to do while loop
} while (again === "Yes");
</script>
</body>
</html>

Answer 1

Scott Sauyet spotted the error location, but mystery == true; should be if (mystery == true) or simply if (mystery) .

Answer 2

The minor changes in this should get you going. It only deals with four genres. There is no handling for mis-typed genres. But the basics are there. The main missing bit was that the else for the Mysteries case was not written correctly.

You will still need to fix one important problem. Note that if the string contains "non fiction" it also contains "fiction", so both of those variables would be true. So there is some testing logic you still need to investigate. If you get stuck on that, ask a separate question showing what you've done and people will be glad to help.

 const FantasyArray = ["The Name of the Wind", "A Wise Man's Fear", "A Game of Thrones", "The Hobbit"]; const MysteryArray = ["A Study in Scarlet", "The Sign of the Four", "The Hound of the Baskervilles"]; const CookingArray = ["The Joy of Cooking", "The Moosewood Cookbook", "The Enchanted Broccoli Forest"]; const SelfHelpArray = ["I Do It Myself!", "Freud for Dummies"] function getRndFromArray(arrayName){ return arrayName[Math.floor(Math.random()*arrayName.length)]; } var again; do { var strng = prompt( "Do you prefer fiction or non fiction books? From here I can choose a genre of book for you to read" ); var fiction = strng.includes("fiction"); var nonfiction = strng.includes("non fiction"); if (fiction == true) { var strng = prompt( "What genre do you prefer from the following? Fantasy, Mystery" ); var fantasy = strng.includes("Fantasy"); var mystery = strng.includes("Mystery"); if (fantasy == true) { alert("I think you will enjoy " +getRndFromArray(FantasyArray)); } else if (mystery == true) { alert("I think you will enjoy " +getRndFromArray(MysteryArray)); } else { //if no option is inputed this set of code will run } } if (nonfiction == true) { var strng = prompt( "What genre do you prefer from the following? Self Help, Cooking" ); var selfhelp = strng.includes("Self Help"); var cooking = strng.includes("Cooking"); if (selfhelp == true) { alert("I think you will enjoy " +getRndFromArray(SelfHelpArray)); } else if (cooking == true) { alert("I think you will enjoy " +getRndFromArray(CookingArray)); } else { //if no option is inputed this set of code will run } } else { again = prompt("You have not told me whether you prefer fiction or non fiction. Would you like to try again? Yes or No?") } } while (again === "Yes"); 

This is a reasonably well-asked question for a newcomer. But there is too much code. Please visit the Help Center , and especially How to create a Minimal, Reproducible Example . You might also want to read How do I create a runnable stack snippet?