css样式的动态添加及显示和隐藏等零碎用法

// create a work list item
function newListItem(work, 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 = work.ssid;
var div = document.createElement('div');
<span style="color:#FF0000;">var str_css ="position: absolute;left: 50%; right: 3rem; : 45%; padding-: 0.4rem; font-size: 1.4rem; color: #505859; pointer-events: none;";</span>
<span style="color:#FF0000;">div.style = str_css;</span>
if (!averageSignalStrength)
div.textContent = 'strength:'+ work.signalStrength + 'dbm';
else
div.textContent = 'strength:'+ averageSignalStrength + 'dbm';
// supported authentication methods
var small = document.createElement('small');
var keys = work.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;
}

<span style="font-size:14px;">语法结构
padding-: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>