简单测验游戏JavaScript

Question

I'm just learning now. Can you please help me, why am I not getting the correct output. This is my code:

//ask questions
var quiz = [
  ["When is Bulgaria established?", 681],
  ["What year was it before 16 years?", 2000],
  ["When does WWII ends?", 1945]
];

//variables
var answer = [];
var correct = [];
var wrong = [];
var correctAns = 0;
var wrongAns = 0;
var oList = "<ol>";

//function to print the result in ordered list
function printResult(result){
  for(var j = 0; j < result.length; j++){
    oList += "<li>" + result[i] + "</li>";
  }
  oList += "</ol>";
  return oList;
}

function print(message) {
  document.getElementById('output').innerHTML = message;
}



//looping, adding correct and wrong answeres
for(var i = 0; i < 3; i++) {
  answer[i] = prompt(quiz[i][0]);
  if(parseInt(answer[i]) == quiz[i][1]){
    correct.push(quiz[i][0]);
    correctAns++;
  } else {
    wrong.push(quiz[i][0]);
    wrongAns++;
  }
}


//print logic
if(correct.length < 1 || correct == undefined){
  print("You did not guess any of the quiestions!");
} else if (correct.length >= 1){
  print("You have guessed " + correctAns + " questions.");
  print(printResult(correct));
  print("You have " + wrongAns + " wrong answeres.");
  if(wrongAns > 0){
    print(printResult(wrong));
  }
}

I have watched this code over and over again and I still can't understand why am I getting undefined as a result. In the debugger, after the loop I check my vars and everything seems ok.

Answer 1

In your printResult function you are using var i instead of j,

Also you better use innerHtml+=message;

 //ask questions var quiz = [ ["When is Bulgaria established?", 681], ["What year was it before 16 years?", 2000], ["When does WWII ends?", 1945] ]; //variables var answer = []; var correct = []; var wrong = []; var correctAns = 0; var wrongAns = 0; //function to print the result in ordered list function printResult(result){ //HERE: var oList = "<ol>"; for(var j = 0; j < result.length; j++){ oList += "<li>" + result[j] + "</li>"; } oList += "</ol>"; return oList; } function print(message) { document.getElementById('output').innerHTML += message; } //looping, adding correct and wrong answeres for(var i = 0; i < 3; i++) { answer[i] = prompt(quiz[i][0]); if(parseInt(answer[i]) == quiz[i][1]){ correct.push(quiz[i][0]); correctAns++; } else { wrong.push(quiz[i][0]); wrongAns++; } } //print logic if(correct.length < 1 || correct == undefined){ print("You did not guess any of the quiestions!"); } else if (correct.length >= 1){ print("You have guessed " + correctAns + " questions."); print(printResult(correct)); print("You have " + wrongAns + " wrong answeres."); if(wrongAns > 0){ print(printResult(wrong)); } } 

 <div id="output"> </div> 

Answer 2

Your main mistake is using i intead of j:

for(var j = 0; j < result.length; j++){
   oList += "<li>" + result[j] + "</li>";// here was i before
}

Answer 3

Basically you have three problems.

• reuse of oList , the variable should be inside declared and used only in printResult .

• Inside of printResult , use of i where j have been used and

• At print , you replace the actual content with new content.

Just a small hint with variable names for counting. It is good practise to start always with i instead of j and go on with the letters in the alphabet.

 var quiz = [["When is Bulgaria established?", 681], ["What year was it before 16 years?", 2000], ["When does WWII ends?", 1945]], answer = [], correct = [], wrong = [], correctAns = 0, wrongAns = 0; //function to print the result in ordered list function printResult(result) { var oList = "<ol>"; // !!! move variable inside of the function for (var j = 0; j < result.length; j++) { oList += "<li>" + result[j] + "</li>"; // !!! use j indstead if i } oList += "</ol>"; return oList; } function print(message) { document.getElementById('output').innerHTML += message; // !!! append message } //looping, adding correct and wrong answeres for (var i = 0; i < 3; i++) { answer[i] = prompt(quiz[i][0]); if (parseInt(answer[i]) == quiz[i][1]) { correct.push(quiz[i][0]); correctAns++; } else { wrong.push(quiz[i][0]); wrongAns++; } } //print logic if (correct.length < 1 || correct == undefined) { print("You did not guess any of the quiestions!"); } else if (correct.length >= 1) { print("You have guessed " + correctAns + " questions."); print(printResult(correct)); print("You have " + wrongAns + " wrong answeres."); if (wrongAns > 0) { print(printResult(wrong)); } }