using jquery to extend textarea
$(document)
.one('focus.textarea', '.autoExpand', function(){
var savedValue = this.value;
this.value = '';
this.baseScrollHeight = this.scrollHeight;
this.value = savedValue;
})
.on('input.textarea', '.autoExpand', function(){
var minRows = this.getAttribute('data-min-rows')|0,
rows;
this.rows = minRows;
rows = Math.ceil((this.scrollHeight - this.baseScrollHeight) / 16);
this.rows = minRows + rows;
});