how to improve performance in jquery

问题

I'm not a good programmer and I just started using jQuery. I need a table sorter that can expand and collapse rows. My code is below. I've spent lots of time trying to improve its execution time. In IE it takes lots of time. I'd appreciate your suggestions.

$(document).ready(function() {
  $('table.sortable').each(function() {
    var $table = $(this);
    var myData = new Array(), myData1 = new Array();
    var rows = $table.find('tbody > tr').get();
    var rowCount = 0;
    $.each(rows, function(index, row){ //arrange rows in 2 dimention array
      if(($(row).children('td').eq(0).attr('class').indexOf('collapse') != -1 || $(row).children('td').eq(0).attr('class').indexOf('expand') != -1)){   
        myData.push(myData1);
        myData1 = [];
      }
      myData1.push(row);    
      rowCount++;
      if(rowCount == $(rows).length){ // to assign last group of rows
        myData.push(myData1);
        myData1 = [];
      }
    });
    $table.find('th').each(function(column) {
      var findSortKey;
      if ($(this).is('.sort-alpha')) {
        findSortKey = function($cell) { 
          return $cell.find('.sort-key').text().toUpperCase() +
            ' ' + $cell.text().toUpperCase();
        };
      }
      else if ($(this).is('.sort-numeric')) {
        findSortKey = function($cell) {
          var key = parseFloat($cell.text().replace(/,/g,''));
          return isNaN(key) ? 0 : key;
        };
      }
      if (findSortKey) {
        $(this).addClass('header').click(function() {
          var newDirection = 1;
          if ($(this).is('.headerSortUp')) {
            newDirection = -1;
          }
          var expand = $table.find('tbody > tr > td.expand').get().length;
          if(expand > 0){
            $.each(myData, function(index, row) {
              $.each(row, function(index1, row2) {
                row2.sortKey = findSortKey($(row2).children('td').eq(column));
              });
            });
            $.each(myData, function(index, row) {
              row.sort(function(a, b) {
                if($(a).children('td').eq(0).attr('class').indexOf('collapse') == -1 && $(a).children('td').eq(0).attr('class').indexOf('expand') == -1 && $(b).children('td').eq(0).attr('class').indexOf('collapse') == -1 && $(b).children('td').eq(0).attr('class').indexOf('expand') == -1 ){
                  return ((a.sortKey < b.sortKey) ? -newDirection : ((a.sortKey > b.sortKey) ? newDirection : 0));
                }
                if(navigator.userAgent.toLowerCase().indexOf('chrome') > -1){
                  return -1; // hack for google chromo
                }
                return 0;
              });
            });
          }else{
            $.each(myData, function(index, row) {
              row.sortKey = findSortKey($(row[0]).children('td').eq(column));
            });
            myData.sort(function(a, b) {
              if (a.sortKey < b.sortKey) return -newDirection;
              if (a.sortKey > b.sortKey) return newDirection;
              return 0;
            });
          }
          // alternate rows goes here and updating table 
          var alt = true;
          var altSub = true;
          $.each(myData, function(index, row) {
            var noRow = $(row).length;
            for (var i=0; i < noRow; i++){
              if($(row[0]).attr('id') == $(row[i]).attr('id')){
                if(alt == true){
                  $(row[0]).removeClass("odd").addClass("even");
                  alt = !alt;
                  altSub =true;
                }else if( alt == false){
                  $(row[0]).removeClass("even").addClass("odd");
                  alt = !alt;
                  altSub = true;
                }
              }else{
                if(altSub == true){
                  $(row[i]).removeClass("alt_row_sub").addClass("alt_row_sub2");
                  altSub = !altSub;
                }else if( altSub == false){
                  $(row[i]).removeClass("alt_row_sub2").addClass("alt_row_sub");
                  altSub = !altSub;
                }
              }
            }
            $table.children('tbody').append(row);
            row.sortKey = null;
          });
          $table.find('th').removeClass('headerSortUp')
            .removeClass('headerSortDown');
          var $sortHead = $table.find('th').filter(':nth-child('
            + (column + 1) + ')');
          if (newDirection == 1) {
            $sortHead.addClass('headerSortUp');
          } else {
            $sortHead.addClass('headerSortDown');
          }
        });
      }
    });
  });
});

image below gives some idea. this wil sort group of rows. table image

回答1:

I'm not entirely sure what you're trying to do, but if you're trying to sort tables, have you considered using this jQuery plugin: http://tablesorter.com/docs/ ?

EDIT: having seen your screenshot (I presume your link should be to: http://www.freeimagehosting.net/uploads/dc95537e24.gif), I see what you're trying to do. This isn't something I've seen in jQuery, but it's something that ExtJS handles very well: http://extjs.com/deploy/dev/examples/grid/grouping.html - that may not be very helpful to you though, sorry.

回答2:

As a start, I would not trying to sort mydata with JavaScript at client-side, but I would to do it a server side. JavaScript is not made for performance and it blocks your browser when it is processing things.

回答3:

Another option to improve performance of operations like sorting data client side is to use the HTML Bridge and interop with a non-visual Silverlight 2 component. That way you can use managed code (C#) to do the calculations client side.

Offcourse you would have to provide a (slower) JavaScript alternative to users who does not have Silverlight 2 installed. Look at this as "progressive enhancement" of performance (use Silverlight if available, if not use JavaScript).

回答4:

Below image is screen shot of the table
demo image

来源：https://stackoverflow.com/questions/974435/how-to-improve-performance-in-jquery