在Web开发中，自动完成功能是一种常见的用户交互方式，它能够根据用户输入的部分信息，自动提供可能的完整信息供用户选择。这种功能可以大大提高用户输入的效率和体验。本文将介绍如何使用JavaScript和ASP Classic实现自动完成功能。
首先，需要创建一个HTML输入框，用于接收用户的输入。同时，还需要一个用于显示建议列表的容器。以下是HTML结构的示例：
<input type="text" id="txtSearchEngines" class="data">
<div id="suggestionBox" style="display:none"></div>
接下来，需要定义一些CSS样式，以美化建议列表的外观。
#suggestionBox {
position: absolute;
z-index: 999;
border: 1px gray solid;
background-color: #E6E6E6;
width: 300px;
}
.suggest-data {
line-height: 20px;
font-family: Tahoma;
font-size: 12px;
}
.rowSelected {
background-color: #415C7C;
color: white;
}
然后，需要编写JavaScript代码来实现自动完成的逻辑。首先，需要绑定事件监听器，以便在用户输入时触发相应的操作。
var xmlhttp, rowToSelect = 0,
searchTextBox = document.getElementById("txtSearchEngines"),
_URL = "AutoSuggest.asp";
BindSearchTextBox();
function BindSearchTextBox() {
searchTextBox.addEventListener("keyup", KeyUpOnSearchTextBox, false);
searchTextBox.addEventListener("keydown", HandleTabKey);
document.getElementsByTagName("body")[0].addEventListener("click", CloseSuggestionBox);
}
在用户输入时，需要根据输入的内容向服务器发送请求，并获取建议列表。以下是发送请求和显示建议的代码示例：
function KeyUpOnSearchTextBox(e) {
var suggestBox = document.getElementById("suggestionBox");
if((e.keyCode >= 65 && e.keyCode <= 90) || (e.keyCode == 40 || e.keyCode == 38 || e.keyCode == 8)) {
searchTextBox.removeEventListener("keyup", KeyUpOnSearchTextBox);
if((e.keyCode == 40 || e.keyCode == 38) && suggestBox.style.display != "none") {
SelectSuggestedRow(e.keyCode == 40 ? 1 : -1);
BindSearchTextBox();
} else {
if(null != searchTextBox.value && "" != searchTextBox.value)
SendAJAXRequestToServer(_URL + "?type=s&searchKey=" + searchTextBox.value, ShowSuggestion, true);
else {
HideSuggestionBox();
BindSearchTextBox();
}
}
} else if(e.keyCode == 13) {
searchTextBox.removeEventListener("keyup", KeyUpOnSearchTextBox);
GetSelectedDetail();
}
}
function ShowSuggestion() {
if(xmlhttp.readyState == 4) {
if(xmlhttp.responseText != "") {
var suggestBox = document.getElementById("suggestionBox"),
suggestRow = document.getElementById("suggest-rows");
suggestBox.style.display = "";
suggestBox.style.top = searchTextBox.offsetTop + searchTextBox.offsetHeight + 2;
suggestBox.style.left = searchTextBox.offsetLeft;
suggestBox.innerHTML = xmlhttp.responseText;
suggestBox.style.display = "";
SelectSuggestedRow(0);
} else HideSuggestionBox();
BindSearchTextBox();
}
}
<%@ Language=VBScript %>
<% Option Explicit %>
<%
'put your security/authenciation code here
Response.Write GetSuggestion
Response.End
Function GetSuggestion()
Dim searchKey
searchKey = Request.QueryString("searchKey")
If searchKey = "g" Then
GetSuggestion = _
"" & _
"" & _
"Google " & _
" " & _
"Google2
"
ElseIf searchKey = "b" Then
GetSuggestion = _
"" & _
"" & _
"Bing
"
End If
End Function
%>