$("textarea.growable")
    .on('keyup paste input', function () {
        let self = $(this);
        let offset = self.innerHeight() - self.height();

        if (self.innerHeight() < this.scrollHeight) {
            //Grow the field if scroll height is smaller
            self.height(this.scrollHeight - offset);
        } else {
            //Shrink the field and then re-set it to the scroll height in case it needs to shrink
            self.height(1);
            self.height(this.scrollHeight - offset);
        }
    });