simple quiz thing

<!DOCTYPE html>
<html>

  <head>
    <link rel="stylesheet" href="style.css">
    <script src="script.js"></script>
  </head>

  <body>
    <button class="test" onClick="test(0)">Take the test</button>
    
  </body>
</html>

var test = (function($test) {
  /*jshint validthis: true */
  "use strict";
  
  var choices = ["a", "b", "c", "d", "e", "f"];
  var warn = "Answer the question!";
  var guide = "Type in the letter indicated next to the answer you want to select";
  
  function Tester(config) {
    //bind all functions in config obj to constructor context so they access to config properties
    for (var p in config) this[p] = typeof config[p] === "function" ? config[p].bind(this) : config[p];
    return this;
  }
  
  function ask(curr, warning) { 
    if (warning) alert(warning);
    if (curr === $test.length) return alert("score: " + this.score + "/" + $test.length + "\r\r" + "review:" + toJson(this.review));
    var question = $test[curr];
    var promptDisp = [ guide, "\r\r", (curr + 1), ". ", question.q, "\r", multipleAnswer(question.c, {}) ].join("");
    var answer = prompt(promptDisp);
    if (!answer || answer === "") return this.ask(curr, warn); //must use this.ask, not ask, since this.ask is a different reference
    if (answer.toLowerCase() === question.a) this.score++;
    this.review.push({ question: question.q, "your answer": answer, "correct answer": question.a  });
    if (curr < $test.length) return this.ask(curr + 1);
  }

  function multipleAnswer(o, tmp) {
    o.forEach(function(c, i) {
      tmp[choices[i]] = c;
    });
    return toJson(tmp);
  }
  
  function toJson(s) {
    return JSON.stringify(s, null, 1).replace(/[\]\[\{\}\,\\"]*/g, "");
  }
  
  function init() {
    var instance = new Tester({
      score: 0,
      review: [],
      ask: ask
    });
    instance.ask(0); //instance.ask already bound to instance context
  }
  
  return init;
  
})([
  
  //answer is multiple choice, a, b, c, d, etc.
  {
    q: "What is 1 + 1?",
    a: "c",
    c: [45, 3, 2]
  },
  {
    q: "Is the earth flat?",
    a: "a",
    c: ["no", "yes"]
  }
  
]);

/* Styles go here */

.test {
  position:absolute;
  left:40%;
  top:30%;
  font-size:45pt;
  font-family:"Helvetica", sans-serif;
  cursor:pointer;
  border:1px solid #848484;
  color:#848484;
  padding:50px;
}

.test:hover {
  border:1px solid black;
  color:black;
}