Get value from text area

Use .val() to get value of textarea and use $.trim() to empty spaces.

$(document).ready(function () {
    if ($.trim($("textarea").val()) != "") {
        alert($("textarea").val());
    }
});

Or, Here's what I would do for clean code,

$(document).ready(function () {
    var val = $.trim($("textarea").val());
    if (val != "") {
        alert(val);
    }
});

Demo: http://jsfiddle.net/jVUsZ/

$('textarea').val();

textarea.value would be pure JavaScript, but here you're trying to use JavaScript as a not-valid jQuery method (.value).

Vanilla JS

document.getElementById("textareaID").value

$("#textareaID").val()

Cannot do the other way round (it's always good to know what you're doing)

document.getElementById("textareaID").value() // --> TypeError: Property 'value' of object #<HTMLTextAreaElement> is not a function

jQuery:

$("#textareaID").value // --> undefined