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JavaScript Object-Oriented JavaScript (2015) Practice Project User Interface Code

Brian Patterson
Brian Patterson
19,588 Points

Getting Uncaught ReferenceError: QuizUI is not defined at app.js:11

I can figures out why I am getting this error

Uncaught ReferenceError: QuizUI is not defined
    at app.js:11

Below is my code for the UI

var QuizUI = {
    displayNext: function () {
        if (quiz.hasEnded()) {
            this.displayScore();
        } else {
            this.displayQuestion();
            this.displayChoices();
            this.displayProgress();
        }
    },
    displayQuestion: function() {
      this.populateIdWithHTML("question", quiz.getCurrentQuestion().text);
      },
  displayChoices: function() {
    var choices = quiz.getCurrentQuestion().choices;
    for(var i = 0; i < choices.length; i++) {
      this.populateIdWithHTML("choice" + i, choices[i]);
      this.guessHandler("guess" + i, choices[i]);
    }
  },
  displayScore:function() {
    var gameOverHTML = "<h1>Game Over</hi>";
    gameOverHTML += "<h2> Your score is: " + quiz.score + "</h2>";
    this.populateIdWithHTML("quiz", gameOverHTML);
  },
  populateIdWithHTML: function(id, text) {
    var button = document.getElementById(id);
    button.onclick = function() {
      quiz.quess(guess);
      QuizUI.displayNext();
    }
  },
  guessHandler: function(id, guess) {
    var button = document.getElementById(id);
    button.onclick = function() {
      quiz.guess(guess);
      QuizUI.displayNext();
    }
  }

  displayProgress: function() {
    var currentQuestionNumber = quiz.currentQuestionIndex + 1;
    this.populateIdWithHTML("progress", "Question " + currentQuestionNumber + " of " + quiz.questions.length);
  }

};

Plus this is my code for the app.js

//Create Questions
var questions = [
    new Question("Who was the first President of the United States?", [ "George Washington", "Thomas Jefferson" ], "George Washington"),
    new Question("What is the answer to the Ultimate Question of Life, the Universe, and Everything?", ["Pi","42"], "42")
];

//Create Quiz
var quiz = new Quiz(questions);

//Display Quiz
QuizUI.displayNext();

Plus, I am getting an uncaught syntax error on line 41 for the ui. Any help would be appreciated.

3 Answers

Steven Parker
Steven Parker
217,626 Points

Without testing it in the actual context, I would expect you might need to explicitly pass "this" and both the item and the index to get the same behavior:

choices.forEach(function(choice, i) {
      this.populateIdWithHTML("choice" + i, choice);
      this.guessHandler("guess" + i, choice);
  }, this);
Brian Patterson
Brian Patterson
19,588 Points

Thanks for that Steven. Two questions why this after the function? Also, I see you have been really helpful on the forums what do you think is the best way to learn? Its one thing understanding it but a completely different ball game apply it.

Steven Parker
Steven Parker
217,626 Points

I think it mostly comes down to practice. The more you use the information you learn, the longer you will retain it and the better you will become at knowing when and how to apply it.

Steven Parker
Steven Parker
217,626 Points

The issue is likely to be in the HTML file. The code for "app.js" is being loaded, but it looks like "QuizUI.js" is not.

If you have trouble pinning down the issue, make a snapshot of your workspace and post the link to it here.

Brian Patterson
Brian Patterson
19,588 Points

I figured it out, Steven. I had legacy code that was interfering with the code he had. I do have one other question though. I am trying to refactor the for-loop. From this:

for(var i = 0; i < choices.length; i++) {
            this.populateIdWithHTML("choice" + i, choices[i]);
            this.guessHandler("guess" + i, choices[i]);
        }

to this:

choices.forEach(function(choice){
          this.populateIdWithHTML("choice" + choice, choice);
          this.guessHandler("guess" + choice, choice)
        });

What is the best what to get this to work with the latest forEach helper for JavaScript? Thanks for your help.