Question

How can I make textbox auto expandable through JavaScript?

Answer 1

You could compare the count of your value with the rows * cols. I dont really know how many letters there are in a col in html but if you tested that you could do something like:

var colCount =  document.yourForm.yourTextArea.cols;
var rowCount =  document.yourForm.yourTextArea.rows;
if((colCount * numberOfLettersInACol) * rowCount) <= document.yourForm.yourTextArea.value.length){
    document.yourForm.yourTextArea.rows = rowCount + 1;
}