Adding functionality for using the up and down arrow keys to select a table row

Question

I need the help of an expert on my question below as it exceed and goes well beyond the level of knowledge that I have for programming in JavaScript.

Given the existing

Answer 1

Here is the complete solution which selects rows in table just like a windows file selection works.

add class multiSelect to you table and then place this code in a JS file

$(document).ready(function() {  
var selectionPivot; 
// code for selected rows. 
$('.multiSelect tbody').on( 'click', 'tr', function (e) {
var tbodyElement = $(this).parents('tbody');
var trElements = tbodyElement.find('tr');
if(!e.ctrlKey && (!e.shiftKey) ){   
  trElements.removeClass("row_selected");
  selectionPivot=$(this);
 } 

if(e.shiftKey){ 
var bot = Math.min(selectionPivot[0].rowIndex, $(this)[0].rowIndex);
var top = Math.max(selectionPivot[0].rowIndex, $(this)[0].rowIndex);
trElements.removeClass("row_selected");
for(var i=bot; i<=top; i++){    
trElements[i-1].className+=" row_selected";
}     
}  
else  { 
   selectionPivot=$(this);
   trElements.removeClass("focus"); 
   $(this).addClass('focus');
    if ( $(this).hasClass('row_selected') ) {
    $(this).removeClass('row_selected');
    }
    else {      
        $(this).addClass('row_selected');
    }
}
});

$(document).keypress(function(evt){
if(evt.shiftKey){
      var highlightedRow = $(".multiSelect .focus");        
      if (highlightedRow.length > 0) // table cell is selected
      {
        var tbodyElement = highlightedRow.parents('tbody');
        var trElements = tbodyElement.find('tr');
        var nextElement =  highlightedRow.next('tr');
        var prevElement = highlightedRow.prev('tr');
        trElements.removeClass("focus");
        switch(evt.keyCode)
        {
          case 40:
            if(nextElement.length)
            {
              nextElement.addClass('row_selected');
              nextElement.addClass('focus');
            }
            else if (trElements.length)
            {
              $(trElements[0]).addClass('row_selected'); 
               $(trElements[0]).addClass('focus');
            }
            break;
          case 38:
            if(prevElement.length)
            {
              prevElement.addClass('row_selected');
              prevElement.addClass('focus');
            }
            else if (trElements.length)
            {
              $(trElements[trElements.length - 1]).addClass('row_selected'); 
                $(trElements[trElements.length - 1]).addClass('focus');
            }
            break;
        }
      }
      }
    });
    });