This will return the padding-left
value:
window.getComputedStyle(txt, null).getPropertyValue('padding-left')
where txt
is the reference to your TEXTAREA element.
The above works in all modern browsers and in IE9. However, it does not work in IE8 and below.
Live demo: http://jsfiddle.net/simevidas/yp6XX/
Further reading: https://developer.mozilla.org/en-US/docs/Web/API/Window/getComputedStyle
Btw, just for comparison, this is how you get the same job done using jQuery:
$(txt).css('padding-left')
The above does work in IE6-8.