Slow performance with a JavaScript + jQuery function to check table row redundancy

Question

I wrote the function using js+jQuery.

Here is a link to a jsFiddle which shows my problem: http://jsfiddle.net/anarnold/LpBaW/

The goal of this function is to scan a table and check for rows that have certain field (td) values matching. Rows then get assigned a class denoting whether or not they are unique, and the number of matching rows are printed into the final field (td) of each row.

It basically uses a nested loop of this structure:

For each row... scan the whole table for matches..

The way I identify rows is to concatenate the field (td) texts from each row into a rowid attribute on the final field (td) for each row.

The current funciton works fine, but it gets very slow with large tables ~2000 rows.

There must be a more efficient and elegant way to accomplish this. Any help would be greatly appreciated!

Answer 1

Here is an example of using an associative array to store the results and then iterate on that:

http://jsfiddle.net/AdDMk/

var rowIdCnt = {};

function unqOrMsgTest() {
    // Store counts here
    var rowIdCnt = {};

    // loop through check tds
    $("#binning tr td[col=check]").each(function() {

        // grab row identifer to check against other rows        
        var rowId = $(this).attr("rowid");

        if (rowId in rowIdCnt) {
            rowIdCnt[rowId] ++;
        } else {
            rowIdCnt[rowId] = 1;
        }

    });

    // Now iterate over each count and update the table appropriately:
    $.each(rowIdCnt, function(rowId, cnt) {
        //this bit of logic picks a class to assign rows        
        var resultClass = "notUnique";
        if (cnt < 2) {
            resultClass = "unique";
        }

        //apply the row class and print the redundancy number into td
        $('#binning tr td[rowid='+rowId+']').text(cnt).parent().addClass(resultClass);

    });

}