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up vote 2 down vote favorite

I need to create an array from tree elements in Javascript and being a newbie I don't know how to achieve this.

pseudo-code :

function make_array_of_tree_node(tree_node)
{
   for (var i = 0; i < tree_node.childCount; i ++) {
      var node = tree_node_node.getChild(i);
      if (node.type ==0) {
         // Here I'd like to put a link (node.title) in an array as an element
      } else if (node.type ==6) {
         // Here the element is a folder so a I need to browse it
         make_array_of_tree_node(node)
      }
   }
}

// Some code
make_array_of_tree_node(rootNode);
// Here I'd like to have access to the array containing all the elements node.title
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1  
Your for loop is missing a close }. –  Mike Samuel Jun 6 '11 at 13:25
    
@Mike Samuel A typo in SO, thank you for noticing it :-) –  Bruno Jun 6 '11 at 14:03
    
@Pointy Thank you for your answer ! –  Bruno Jun 6 '11 at 14:03
    
You are most welcome. Best of luck! –  Pointy Jun 6 '11 at 14:11
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1 Answer

up vote 1 down vote accepted

You can declare an array like this:

var nodes = [];

Then you can add things to it with:

nodes.push(something);

That adds to the end of the array; in that sense it's kind-of like a list. You can access elements by numeric indexes, starting with zero. The length of the array is maintained for you:

var len = nodes.length;

What you'll probably want to do is make the array another parameter of your function.

edit — To illustrate the pattern, if you've got a recursive function:

function recursive(data, array) {
  if ( timeToStop ) {
    array.push( data.whatever );
  }
  else {
    recursive(data.subData, array);
  }
}

Then you can use a second function to be the real API that other code will use:

function actual(data) {
  var array = [];
  recursive(data, array); // fills up the array
  return array;
}

In JavaScript, furthermore, it's common to place the "recursive" function inside the "actual" function, which makes the recursive part private and keeps the global namespace cleaner.

share|improve this answer
    
You can also add something to an array in JS with nodes[nodes.length] = theItem –  josh.trow Jun 6 '11 at 13:26
    
@josh.trow yes that's true. –  Pointy Jun 6 '11 at 13:29
    
But declaring the array in the function is going to erase the previous one, no ? –  Bruno Jun 6 '11 at 13:31
    
Yes - that's why I said you should make the array a parameter to the function. When you call the function, pass in the array. A common pattern is to wrap your function in an "outer" function. I'll update my answer ... –  Pointy Jun 6 '11 at 13:36
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