jQuery add or remove table row based on inputs

Question

Sorry, if this is too basic.

1. I am trying to add rows to a table if current number of rows are less than a user\'s demand.
2. At the same time, I need t

Answer 1

At these situations jQuery excels, let us play with all sort of selectors. First you need to separate the header and body of the table (thead and tbody). (Code not tested).

function refresh(new_count) {
//how many applications we have drawed now ?
var old_count = parseInt($('tbody').children().count());
//the difference, we need to add or remove ?
var rows_difference = parseInt(new_count) - old_count;
//if we have rows to add
if (rows_difference > 0)
{
    //$('tbody').append() or prepend() new empty rows based on your pattern with a loop
}
else if (rows_difference < 0)//we need to remove rows ..
{
    var index_start = old_count - rows_difference;//for the LAST X rows
    $('tr:gt('+index_start+')').remove();
}
}

Answer 2

I took the ideas presented by @B3aT, edited, and fleshed out to make this (available at my fork of OP's jsfiddle:

var row_i = 0;

function emptyRow() {
  row_i++;
  this.obj = $("<tr></tr>");
  this.obj.append('<td><input type="text" size="5" value="' + row_i + '"/></td>');
  this.obj.append('<td><input type="text" size="5" name="mm' + row_i + '" id="id_mm' + row_i + '""/></td>');
  this.obj.append('<td><input type="text" size="5" name="dd' + row_i + '" id="id_dd' + row_i + '""/></td>');
  this.obj.append('<td><input type="text" size="5" name="ma' + row_i + '" id="id_ma' + row_i + '""/></td>');
  this.obj.append('<td><input type="text" size="5" name="sr' + row_i + '" id="id_sr' + row_i + '" value="0""/></td>');
}

function refresh(new_count) {
  if(new_count > 0) {
    $("#noa_header").show();
  }
  else {
    $("#noa_header").hide();
  }
  var old_count = parseInt($('tbody').children().length);

  var rows_difference = parseInt(new_count) - old_count;

  if (rows_difference > 0)
  {
     for(var i = 0; i < rows_difference; i++)
        $('tbody').append((new emptyRow()).obj);
  }
  else if (rows_difference < 0)//we need to remove rows ..
  {
     var index_start = old_count + rows_difference + 1;          
     $('tr:gt('+index_start+')').remove();
     row_i += rows_difference;
  }
}

$(document).ready(function () {
    $('#id_noa').change(function () {
        refresh( $(this).val() );
    })
});

The reason the emptyRow function is so long is that I wanted to make the number of columns easy to manipulate. Each column is appended individually, so changing the default pattern is simple.

In the html, I had to add the thead and tbody tags as described in @B3aT's answer. The thead includes the first two rows, because row 1 is the select box and row 2 is the actual header for the table. The tbody is empty to start.

As far as changing styles for individual rows (like adjusting column width), you'd be better off not using a table. Table-like behavior can be as simple as using float:left in your column style, making sure to place a div with clear:both at the end of each row.