<label for="leaveword">留言</label>

<textarea name="" placeholder="點選給商家留言" id="textarea" cols="30" rows="1" class="bianji-textarea-l" autoHeight="true"></textarea>

$(function(){

$.fn.autoHeight = function(){

function autoHeight(elem){

elem.style.height = 'auto';

elem.scrollTop = 0; //防抖動

elem.style.height = elem.scrollHeight + 'px';

}

this.each(function(){

autoHeight(this);

$(this).on('keyup', function(){

autoHeight(this);

});

});

}

$('textarea[autoHeight]').autoHeight();

})