Saving Bookmark Node Info To a Global Array

**misfitplanet** · 05-06-2011, 07:18 AM

This has been solved with a hack (setting a timeout that waits for the callbacks to finish in the chrome). I didn't know this about JavaScript, that it will jump over code before it finishes other code when dealing with callbacks.. I only knew this to occur with threads in other languages. Maybe a thread is created in the Chrome? Please help me with a better answer if you know.

I'm writing a bookmark manager extension. I've found a way to see the id, title and urls of bookmarks through console, but i need the info saved for further processing in a global array. I placed the global in the loop, but the call back function seems not ignore the global, erase it, or something. The data is not being stored in it. Is there a workaround for this? New to JavaScript.

Code:

function printBookmarks(bookmarks) {
  bookmarks.forEach(function(bookmark) {
    console.debug(bookmark.id + ' - ' + bookmark.title + ' - ' + bookmark.url);
    bookmarkEntries = bookmarkEntries.concat([bookmark.id + ' - ' + bookmark.title + ' - ' + bookmark.url]);  // why are bookmarks not being added to global ??
    if (bookmark.children)
      printBookmarks(bookmark.children);
  });
}

function setBookmarkData()
{
    bookmarkEntries = []
    chrome.bookmarks.getTree(function(bookmarks) {
    printBookmarks(bookmarks);
});
    alert(bookmarkEntries) // comes up as empty array ???
}

If you'd like to take a peek at it I have the JavaScript running on a server now. http://75.72.25.11

**devnull69** · 05-06-2011, 10:22 AM

Hm I don't trust .concat() here because sometimes it tends to create references instead of copies. And those references are lost after the callback finishes.
Try this instead:

Code:

bookmarkEntries.push(bookmark.id + ' - ' + bookmark.title + ' - ' + bookmark.url);

And initiate the array in the global scope rather than inside a function

Code:

var bookmarkEntries = [];
function setBookmarkData() {
   chrome.bookmarks.getTree(function(bookmarks) {
      printBookmarks(bookmarks);
   });
   alert(bookmarkEntries) // comes up as empty array ???
}

**misfitplanet** · 05-06-2011, 04:30 PM

Made the changes, but still no data saved inside the global. This is really frustrating to see it there is the console, then pushing it to the global, yet the global comes up empty. Any other ideas?

Code:

var bookmarkEntries = []
//also tried   bookmarkEntries without var, no avail

function printBookmarks(bookmarks) {
  bookmarks.forEach(function(bookmark) {
    console.debug(bookmark.id + ' - ' + bookmark.title + ' - ' + bookmark.url);
    bookmarkEntries.push([bookmark.id + ' - ' + bookmark.title + ' - ' + bookmark.url]);
    if (bookmark.children)
      printBookmarks(bookmark.children);
  });
}

function setBookmarks()
{
    bookmarkEntries = []
    chrome.bookmarks.getTree(function(bookmarks) {
    printBookmarks(bookmarks);
});
    alert(bookmarkEntries);
}

**misfitplanet** · 05-06-2011, 05:04 PM

Here is minified extension code, code just to point out the problem. You could either place these to files in a folder and load load as an extension or download a ready-to-load example from my gmail docs.

https://docs.google.com/leaf?id=0B6u...ZDkyM2Ji&hl=en

Code:

{
  "name": "Bookmarks Ext",
  "version": "0.1",
  "incognito": "split",
  "chrome_url_overrides": {
    "bookmarks": "index.html"
  },
  "permissions": [
  "bookmarks",
  "bookmarks.getChildren",
  "bookmarks.getTree",
  "bookmarks.id",
  "bookmarks.title",
  "bookmarks.url"
]
}

Code:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
    "http://www.w3.org/TR/html4/strict.dtd"
    >
<html lang="en">
<head>
    <script type="text/javascript">
        
        function setBookmarkEntries()
        {
            chrome.bookmarks.getTree(function(bookmarks) {
            printBookmarks(bookmarks);});
        }
            
        function printBookmarks(bookmarks) {
            bookmarks.forEach(function(bookmark) {
            console.debug(bookmark.id + ' - ' + bookmark.title + ' - ' + bookmark.url);
            bookmarkEntries.push([bookmark.id + ' - ' + bookmark.title + ' - ' + bookmark.url]);
            if (bookmark.children)
                printBookmarks(bookmark.children);});
        }
    </script>
</head>
<body>
    <script type="text/javascript">
        bookmarkEntries = []
        setBookmarkEntries()
        alert("Bookmark Entries: " + JSON.stringify(bookmarkEntries));
    </script>
</body>
</html>

**devnull69** · 05-08-2011, 07:19 AM

Originally Posted by misfitplanet

[COLOR="red"]This has been solved with a hack (setting a timeout that waits for the callbacks to finish in the chrome). I didn't know this about JavaScript, that it will jump over code before it finishes other code when dealing with callbacks.

Ok sorry, I did not see that in your post because of the unusual indentation you use.

BUT: It is a general property of callbacks not only in Javascript. It is called "asynchronous execution" and yes, it will create threads in the background process. Most of the functions provided in the Chrome Extension System are being executed asynchronously. It is never good to use setTimeout to care for this though. Just put everything depending on the result of the callback INSIDE the callback.

Code:

function printBookmarks(bookmarks) {
   bookmarks.forEach(function(bookmark) {
      console.debug(bookmark.id + ' - ' + bookmark.title + ' - ' + bookmark.url);
      bookmarkEntries = bookmarkEntries.concat([bookmark.id + ' - ' + bookmark.title + ' - ' + bookmark.url]);  // why are bookmarks not being added to global ??
      if (bookmark.children)       printBookmarks(bookmark.children);
   });
}

function setBookmarkData() {
   bookmarkEntries = [];
   chrome.bookmarks.getTree(function(bookmarks) {
      printBookmarks(bookmarks);
      alert(bookmarkEntries) // comes up as empty array ???
   });
}

Yes, it's as easy as that

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