Javascript code too slow in Firefox extension using Storage service

Question

I\'m running the following javascript code in firefox extension

highlightLinks: function(e) {

  var anchors = e.target.getElementsByTagName(\"a\");
  let file =         


        

Answer 1

In general when you call a database(not the browser ones) it is better to make one call, fetch all the data you will need into an array or an hash, and then work with them internally.

EDIT:

I would do that: load from the storage all the links and build a hash like:

linksHash = {
  'url-1':true,
   ...,
  'url-n':true
}

Then loop on anchors and make a check with something like:

if(linksHash[anchors[i].href]){
 //the link href is in the hash
}

Then if you note the RAM becomes an issue cut the load of the table in 2 or more pieces.

Answer 2

first tip, altough it won't save too much time, is not using anchors.length in the condition of the for-loop. better use:

for(var i = 0, num = anchors.length; i < num, i++) {...}

Answer 3

It'll be faster if you pull the createStatement out of the loop, and reuse it, rebinding the parameters each time. The docs for storage say: "Note: If you need to execute a statement multiple times, caching the result of createStatement will give you a noticeable performance improvement because the SQL query does not need to be parsed each time."

So instead of:

for (var i = 0; i < anchors.length; i++) {
  var statement = conn.createStatement("select * from links where url=?1");
  statement.bindStringParameter(0, anchors[i].href);
  // ... do stuff with results

write:

var statement = conn.createStatement("select * from links where url=?1");
for (var i = 0; i < anchors.length; i++) {
  statement.bindStringParameter(0, anchors[i].href);
  // ... do stuff with results

Edit: Also, if you're using a recent Firefox, you can use their asynchronous API to avoid delaying the UI. Instead of calling executeStep, use executeAsync instead.

statement.executeAsync({
  handleResult: function(aResultSet) {
    // ... do stuff with results
  },

  handleError: function(aError) {
    print("Error: " + aError.message);
  },

  handleCompletion: function(aReason) {
    if (aReason != Components.interfaces.mozIStorageStatementCallback.REASON_FINISHED)
      print("Query canceled or aborted!");
  }
});