Question

I have a function that is called on document.ready that loops through a table with roughly 600 rows that was generated in classic ASP. In a “modern” browser (Chrome, Firefox, IE9 Beta) it runs in under 1.5-2 seconds. In IE6 it runs in around 5-7 seconds, not good.

Basically what I’m doing is adding the value of the cells in certain columns and giving subtotals. (I know, this should be generated on the server-side, but some brainiac developed this using views that calls views, who call views, who call views…).

I used IE9’s profiler to try to get a sense of where a bottle neck is and it seems to be most profound when jQuery’s find and each is called:

tr.find("td").each(function() {
&
tr.find("td").eq(ci).html(tot).css

I will post all of the code if necessary but I was wondering is there a more efficient way of looping through unnamed table rows and cells?

The table looks like:

32     47       0/0 0 8 1 1                 
32     47  -7   0/0 0 0   7 
Totals     -7   0/0   8 1 8  
32     47       0/0 0 2 1 1                 
32     47  -7   0/0 0 3   7 
Totals     -7   0/0   5 1 8  

I loop through the table rows and if I find a (td:first) = “Totals” then I place the current tr, and the two previous tr’s in variables, then grab cells and calculate totals, and place those totals in the appropriate cells.

This all works but like I said there is a serious bottle neck during find and each.

Answer 1

I haven’t tested it myself, but it’s possible that all the jQuery extensions are what’s slowing things down. Try doing this with plain javascript and see if it speeds things up:

var rows = document.getElementById('your-table').rows;
var num_rows = rows.length;
for (var i = 0; i < num_rows; ++i) {
    var cells = rows[i].cells;
    if (cells[0].innerHTML == 'Totals') {
       var num_cells = cells.length;
       for (var j = 1; j < num_cells; ++j) {
           cells[j].innerHTML =
               (parseInt(rows[i-2].cells[j]) || 0) +
               (parseInt(rows[i-1].cells[j]) || 0);
       }
    }
 }