Create an array with tree elements in Javascript

Question

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

Your for loop is missing a close }.

Mike Samuel
– Mike Samuel

2011-06-06 13:25:34 +00:00
Commented Jun 6, 2011 at 13:25 — Mike Samuel
– Mike Samuel, Commented Jun 6, 2011 at 13:25
@Mike Samuel A typo in SO, thank you for noticing it :-)

Bruno
– Bruno

2011-06-06 14:03:29 +00:00
Commented Jun 6, 2011 at 14:03 — Bruno
– Bruno, Commented Jun 6, 2011 at 14:03

Pointy · Accepted Answer · 2011-06-06 13:38:29Z

2

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.

edited Jun 6, 2011 at 13:38

answered Jun 6, 2011 at 13:24

Pointy

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3 Comments

josh.trow Over a year ago

You can also add something to an array in JS with nodes[nodes.length] = theItem

Bruno Over a year ago

But declaring the array in the function is going to erase the previous one, no ?

Pointy Over a year ago

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 ...

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