如何使用javascript从TextArea获取值？

Question

Well this question might look simillar to questions easily findable with google but for some reason all solutions out there have not worked for me. All I want to do is to check if there is text inside of textarea.

JS snippet:

var PrzedDzier = document.getElementById('ctl00_m_g_87871370_ce46_4f47_b1eb_614d0106535d_ff105_1_ctl00_ctl00_TextField');   
var a = PrzedDzier.val();
if(a == "")
{
  alert('FU');
  result = false;
}

HTML baby:

<textarea dir="none" class="ms-long" title="PDzier" id="ctl00_m_g_87871370_ce46_4f47_b1eb_614d0106535d_ff105_1_ctl00_ctl00_TextField" cols="20" rows="2" name="ctl00$m$g_87871370_ce46_4f47_b1eb_614d0106535d$ff105_1$ctl00$ctl00$TextField"></textarea>

Debugger (Firebug) stops working at var a = PrzedDzier.val(); so I assume it's something wrong with val() method...

Answer 1

You have retrieved the object as a JS object, not a jQuery object. You need to use the jQuery ID selector to retrieve the jQuery object:

var PrzedDzier = $("#ctl00_m_g_87871370_ce46_4f47_b1eb_614d0106535d_ff105_1_ctl00_ctl00_TextField");
var a = PrzedDzier.val();
if(a == "")
{
  alert('FU');
  result = false;
}

If you would like to access the text using pure JS, simply use the value property:

PrzedDzier = document.getElementById('ctl00_m_g_87871370_ce46_4f47_b1eb_614d0106535d_ff105_1_ctl00_ctl00_TextField');   
var a = PrzedDzier.value;
if(a == "")
{
  alert('FU');
  result = false;
}

Answer 2

Since you are using jQuery you can directly access the textarea and get the value as below.

$("#ctl00_m_g_87871370_ce46_4f47_b1eb_614d0106535d_ff105_1_ctl00_ctl00_TextField").val();

But usually, it is more error prone to get an element using its runtime ID (if there are easy chances that the element would be moved which would change the runtime ID), otherwise you can very well use the above code.

Answer 3

I believe using strlen is better than comparing with "" because strlen is much faster and "" takes 6 bytes of ram.just letting you know the other way

var j = document.getElementById('idoftextbox').value;
 if (strlen(j) == 0) 
  {
    alert('FU');
    return false;
  }