Pouvez vous m'aider à comprendre une fonction

var current_index = 0 ;

var questionnaireEN = new Array();
 
//QUESTION 1
questionnaireEN[0] = new Array();
questionnaireEN[0][0] = "Comment dit-on jaune en anglais ?";
questionnaireEN[0][1] = "images/EnQuiz1";
questionnaireEN[0][2] = new Array("yellow","red","cat","blue");

questionnaireEN[0][3] = "yellow";
 
 
//QUESTION 2
questionnaireEN[1] = new Array();
questionnaireEN[1][0] = "Comment dis-tu ton prénom en anglais?";
questionnaireEN[1][1] = "images/monImage.png";
questionnaireEN[1][2] = new Array("I am...","I live in...","My name is...","Blue...");

questionnaireEN[1][3] = "My name is...";
 
 
//QUESTION 3
questionnaireEN[2] = new Array();
questionnaireEN[2][0] = "Comment dit-tu le chffre trois en anglais? ";
questionnaireEN[2][1] = "images/monImage.png";
questionnaireEN[2][2] = new Array("one","two","blue","three");

questionnaireEN[2][3] = "three";

//QUESTION 4
questionnaireEN[3] = new Array();
questionnaireEN[3][0] = "Comment dit-on salut en anglais ?";
questionnaireEN[3][1] = "images/EnQuiz1";
questionnaireEN[3][2] = new Array("november","yes","blue","hello");

questionnaireEN[3][3] = "hello";
 
//QUESTION 5
questionnaireEN[4] = new Array();
questionnaireEN[4][0] = "Comment dit-on cochon en anglais ?";
questionnaireEN[4][1] = "images/EnQuiz1";
questionnaireEN[4][2] = new Array("cow","pig","birds","blue");

questionnaireEN[4][3] = "pig";

//QUESTION 6
questionnaireEN[5] = new Array();
questionnaireEN[5][0] = "Comment dit-on septembre en anglais ?";
questionnaireEN[5][1] = "images/EnQuiz1";
questionnaireEN[5][2] = new Array("january","july","august","september");

questionnaireEN[5][3] = "september";

//QUESTION 7
questionnaireEN[6] = new Array();
questionnaireEN[6][0] = "Comment dit-on Je vis à... en anglais ?";
questionnaireEN[6][1] = "images/EnQuiz1";
questionnaireEN[6][2] = new Array("I like to do...","I live in...","I was born in...","My name is...");

questionnaireEN[6][3] = "I live in...";

//QUESTION 8
questionnaireEN[7] = new Array();
questionnaireEN[7][0] = "Comment dit-on ours en anglais ?";
questionnaireEN[7][1] = "images/EnQuiz1";
questionnaireEN[7][2] = new Array("dog","fish","blue","bears");

questionnaireEN[7][3] = "bears";

//QUESTION 9
questionnaireEN[8] = new Array();
questionnaireEN[8][0] = "Comment dit-on marron en anglais ?";
questionnaireEN[8][1] = "images/EnQuiz1";
questionnaireEN[8][2] = new Array("grey","black","brown","white");

questionnaireEN[8][3] = "brown";

//QUESTION 10
questionnaireEN[9] = new Array();
questionnaireEN[9][0] = "Comment dit-on poney en anglais ?";
questionnaireEN[9][1] = "images/EnQuiz1";
questionnaireEN[9][2] = new Array("november","i live in...","poney","blue");

questionnaireEN[9][3] = "poney";

function compare(a,b){
    var alert ;
 if (a == b){
  alert=("Bravo ! C'est la bonne reponse, passons a la question suivante ! ");
     
  if ( current_index+1 == questionnaireEN.length){
   alert=("Questionnaire Finis, on revient au debut");
   show_quizz(0);
  }else{
   show_quizz((current_index+1));
  }
 }else{
  alert=("Dommage, c'est une mauvaise reponse ! Essaye encore !");
 }
    document.getElementById("phrase").innerHTML = alert
}
 function show_quizz(index){
current_index = index;
document.getElementById("question").innerHTML = questionnaireEN[index][0];

reponses = document.getElementById("reponses");
reponses.innerHTML = "";
for (var i = 0; i < questionnaireEN[index][2].length ; i++){
 reponses.innerHTML += "<input type='button' value='"+questionnaireEN[index][2][i]+"' onclick=\"compare(\'"+questionnaireEN[index][2][i]+"\',\'"+questionnaireEN[index][3]+"\');\" />  " ;

  
    
}
 
}