查找div中的行数

你的代码的问题是，如果你没有指定行高，line-height的默认值是normal。

$(function() {
  var divheight = $("#startegy-sections-targeting-exclude").height();
  var lineheight = parseInt($("#startegy-sections-targeting-exclude").css('line-height'), 10);
  console.log("Number of lines:", Math.round(divheight / lineheight));
});

#startegy-sections-targeting-exclude {
  line-height: 20px;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<div id="startegy-sections-targeting-exclude">
  3PAS-Pub-IO-doubleclick.net-LI, ATOM_DFP_Pub_LI, AUG12_Zynga.com_MafiaWars2_0.10$_CPM, ATOM_Macro_Jivox Testing, Sep 11 Head and Shoulder Innovation - Do Not Bill, 123Greetings - IN Do Not Pay_Second, July 11_Affinity.com_Fiat Linea_CPL 55, 3PAS-Pub-IO-atdmt.com-LI,
  2_Affinity_RealEstate_CPC_2.8_INR_2nd, AUG12_Zynga.com_treasureIsle_0.10$_CPM, AUG12_Zynga.com_theville_0.10$_CPM, 123Greetings - IN Do Not Pay_NonIndia, AUG12_Zynga.com_RubyBlast_0.10$_CPM, 12_Affinity_Education_CPC_2.8_INR_1st, 728x90_Original, 300x250_TagModified,
  Dec11_ WhyteFort_CPL_INR 45, AUG12_Zynga.com_PetsVille_0.10$_CPM, 123Greetings - IN Do Not Pay_First, AUG12_Zynga.com_FishVille_0.10$_CPM, 3PAS-Pub-IO-adfac.net-LI, 3PAS-Pub-IO-bs.serving-sys.com-LI1, 3PAS-test-pub-IO-li, 160x600_Noscr...
</div>

你可以使用jQuery的ThreeDots插件:http://tpgblog.com/2009/12/21/threedots-the-jquery-ellipsis-plugin/

在<div>上呼叫ThreeDots()时，将max_rows设置为4。只要看看那个页面上的例子，你也可以设置自定义的"阅读更多"链接。但要注意，你必须把你的文本包装成一个额外的<span>，像这样:

<div class="text_here">
    <span class="ellipsis_text">
        your text
    </span>
</div>

…jQuery代码行应该是:

$('.text_here').ThreeDots({ max_rows:4 });

如果没有指定行高，就不应该使用$("#startegy-sections-targeting-exclude").css('line-height');。在javascript中，你可以这样写:

var element = document.getElementById('startegy-sections-targeting-exclude');
var lineheight = document.defaultView.getComputedStyle(element, null).getPropertyValue("lineHeight");