分配对象的参数值javascript

Question

I have been looking at this code for a long time trying to figure this out, but I am having no luck. This issue is that I want to assign a value to the parameter boxId. When I click on a box in the webpage an alert will come up displaying that id. I have tried many things, but nothing seems to work. I'm a beginner, so I feel at this point there just must be something that I don't know how to do.

constructor function:

 function Box (boxId, name, color, number, coordinates) {  
   this.boxId = boxId;
   this.name = name;
   this.color = color;
   this.number = number;
   this.coordinates = coordinates;
  }

global variables:

  var boxes = []; 
  var counter = 0; 
  var boxId = 0;

init function:

  window.onload = init;

  function init() {     
   var generateButton = document.getElementById("generateButton");
   generateButton.onclick = getBoxValues;   
   var clearButton = document.getElementById("clearButton");
   clearButton.onclick = clear;   
  }

function to get values and create new boxes:

  function getBoxValues() {
   var nameInput = document.getElementById("name");  
   var name = nameInput.value; 

   var numbersArray = dataForm.elements.amount;
   for (var i = 0; i < numbersArray.length; i++) {
   if (numbersArray[i].checked) {
     number = numbersArray[i].value;
   }
   }  

   var colorSelect = document.getElementById("color");  
   var colorOption = colorSelect.options[colorSelect.selectedIndex];  
   var color = colorOption.value;                       

   if (name == null || name == "") {                    
     alert("Please enter a name for your box");
     return;
   }
   else {
    var newbox = new Box(boxId, name, color, number, "coordinates");  
    boxes.push(newbox);
    counter++;
    var boxId = counter;
    }

    addBox(newbox);

   var data = document.getElementById("dataForm");               
    data.reset();
   }

function that adds boxes to the page:

 function addBox(newbox) {  
   for (var i = 0; i < newbox.number; i++) {                            
   var scene = document.getElementById("scene");              
   var div = document.createElement("div");                   
   div.className += " " + "box"; 
   div.innerHTML += newbox.name; 
   div.style.backgroundColor = newbox.color; 
   var x = Math.floor(Math.random() * (scene.offsetWidth-101));
   var y = Math.floor(Math.random() * (scene.offsetHeight-101));
   div.style.left = x + "px";
   div.style.top = y + "px"; 
   scene.appendChild(div); 
   div.onclick = display;                         
    }                  
  }

function to display alert when box is clicked:

  function display(e) {
  var a = e.target;
  alert(a.counter);
  }

function to clear boxes:

function clear() {
  var elems = document.getElementsByClassName("box");
  for ( k = elems.length - 1; k >= 0; k--) {
   var parent = elems[k].parentNode;
   parent.removeChild(elems[k]);
  }
  }

All of the other functions work just fine. I keep running into the id showing up as "undefined" when I click it, or the counter displaying "0" in the console log, for everything I've tried.

Answer 1

You can do it like this.

First, in addBox() embed boxId as an tag's attribute like this:

div.setAttribute('data-boxId', newbox.boxId);

Then in display() you can retrieve it back:

alert(e.target.getAttribute('data-boxId'));

Please tell if you do not prefer this approach and I will post an alternative (closure things).

Edit: Add jsfiddle example http://jsfiddle.net/runtarm/8FJpU/

Answer 2

One more try. Perhaps if you change:

var boxId = counter;

to

boxId = counter;

It will then use the boxId from the outer scope instead of the one defined in the function getBoxValues()