样式的动态添加：

（其中红色字体是动态添加样式的语句），这是一个动态生成无序列表的函数，用来显示搜索到的wifi信号，其中有3个参数，wifi的名称、加密方式、信号强度。

// create a network list item

function newListItem(network, averageSignalStrength) {

/**

* A Wi-Fi list item has the following HTML structure:

* <li>

* <div>"signalStrength"+ dbm</div>

* <small> Network Security </small>

* <a [class="wifi-secure"]> Network SSID </a>

* </li>

*/

// ssid

var _ = navigator.mozL10n.get;

var ssid = document.createElement('a');

ssid.textContent = network.ssid;

var div = document.createElement('div');

<span>var str_css ="position: absolute;left: 50%; right: 3rem; top: 45%; padding-top: 0.4rem; font-size: 1.4rem; color: #505859; pointer-events: none;";</span>

<span>div.style = str_css;</span>

if (!averageSignalStrength)

div.textContent = 'strength:'+ network.signalStrength + 'dbm';

else

div.textContent = 'strength:'+ averageSignalStrength + 'dbm';

// supported authentication methods

var small = document.createElement('small');

var keys = network.capabilities;

if (keys && keys.length) {

small.textContent = _('securedBy', { capabilities: keys.join(', ') });

small.textContent = keys.join(', ');

} else {

small.textContent = _('securityOpen');

small.dataset.l10nId = 'securityOpen';

}

// create list item

var li = document.createElement('li');

li.appendChild(div);

li.appendChild(small);

li.appendChild(ssid);

return li;

}

样式的显示和隐藏：

遍历标签 exp = document.getElementById("exp");

隐藏标签 exp.style.display = "none";

显示标签 exp.style.display = "list-item";

Padding 属性定义元素边框与元素内容之间的空间。

padding 简写属性在一个声明中设置所有内边距属性。设置所有当前或者指定元素内边距属性。该属性可以有1到4个值

<span>语法结构

padding-top:20px;上内边距

padding-right:30px;右内边距

padding-bottom:30px;下内边距

padding-left:20px;左内边距

padding:1p四边统一内边距

padding:1px1px上下,左右内边距

padding:1px1px1px上,左右,下内边距

padding:1px1px1px1px上,右,下,左内边距</span>