The all collection includes one element object for each valid HTML tag.
If a valid tag has a matching end tag, both tags are represented by the same element object.
all集合包含每个有效标签构成的元素对象。
是由微软增加的，IE11不再支持all集合，其他浏览器也支持此对象，能不用尽量不要用。
例子：
<!DOCTYPE html> <html> <head> <title>validation</title> <meta charset="utf-8" /> <script type="text/javascript"> window.onload = function() { var html = "<table border='1' style='font-size:12px;'>"; function getElement(sec) { if (sec) { html += "<tr><td>" + sec + "</td>" + "<td>" + eval(sec).tagName + "</td>"; } } getElement("document.all(0)"); getElement("document.all[0]"); getElement("document.all.item(0)"); getElement("document.all('SPAN1')"); getElement("document.all.SPAN1"); getElement("document.all['SPAN1']"); getElement("document.all.namedItem('SPAN1')"); html += "</table>"; var names = "<br>"; for (var i = 0; i < document.all.length ; i++) { names += document.all[i].tagName + ": " + document.all[i].id + "; "; } document.getElementById("names").innerHTML = html + names; } </script> </head> <body id="aaa"> <span id="SPAN1"></span> <div id="info"> <div id="names"> </div> </div> </body> </html>
上面的结果是：
