程序说明【select】
先说清空一个select,最简单的方法是把options的length设为0就可以了:
oSelect.options.length = 0;
给select添加option,有多个方法,如果用dom的标准方法是:
js代码:
var op = document.createElement("option"); op.value = i; op.innerHTML = i; oSelect.appendChild(op);
对于option有更方便的方法:
Js代码:
oSelect.options.length = iLength; for (var i = 0; i < iLength; i++){
oSelect.options[i].text = oSelect.options[i].value = iStart + i;
}
其中new Option的第一个参数是显示的文本值,第二个是value值。
利用options.add的第二个可选参数可以把options插入到指定的索引位置,还有一个remove方法可以移除指定索引的options。
要注意的是options下标从0开始。
不过我这里用了一个看来比较笨的方法:
Js代码:
oSelect.options.length = iLength; for (var i = 0; i < iLength; i++) { oSelect.options[i].text = oSelect.options[i].value = iStart + i; }
别看这么笨,却是最有效率的,而且不用每次都清空select,下面可以测试一下:
下面是完整测试代码:
JS代码:
<%@ page language="java" import="java.util.*" pageEncoding="gb2312"%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=gb2312" /> <title>测试效率</title> <select id="testSel"></select> <div id="testShow"></div> <input name="" type="button" value="效率测试" id="testBtn" /> <script> //笨方法 document.getElementById("testBtn").onclick = function(){ var testSel = document.getElementById("testSel"), testShow = document.getElementById("testShow"), iMin = 0, iMax = 1000, dt; testShow.innerHTML = ""; dt = new Date().getTime(); var len = iMax - iMin + 1; testSel.options.length = len; for (var i = 0; i < len; i++) { testSel.options[i].text = testSel.options[i].value = iMin + i; } testShow.innerHTML += "笨方法:" + (new Date().getTime() - dt) + " 毫秒;"; //new Option方法 dt = new Date().getTime(); testSel.options.length = 0; for (var i = iMin; i <= iMax; i++) { testSel.options.add(new Option(i, i)); } testShow.innerHTML += "new Option方法:" + (new Date().getTime() - dt) + " 毫秒;"; //dom方法 dt = new Date().getTime(); testSel.options.length = 0; for (var i = iMin; i <= iMax; i++) {
var op = document.createElement("option"); op.value = i; op.innerHTML = i;
testSel.appendChild(op);
} testShow.innerHTML += "dom方法:" + (new Date().getTime() - dt) + " 毫秒;"; } </script> </html>
测试结果如下|:
还有一个更快的方法,就是使用outerHTML,但这个会对select本身操作而且不兼容就不推荐了。
最后实现|:JavaScript html js日期连动,自动判断是否闰年,判断当前月份天数
首先是实例化一个DateSelector,其中三个参数分别是年月日的select对象。
可选参数:
Year: 0,//年
Month: 0,//月
Day: 0,//日
MinYear: 0,//最小年份
MaxYear: 0,//最大年份
onChange: function(){}//日期改变时执行
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=gb2312" /> <title>日期联动选择器</title> <script type="text/javascript"> var $ = function (id) { return "string" == typeof id ? document.getElementById(id) : id; }; function addEventHandler(oTarget, sEventType, fnHandler) { if (oTarget.addEventListener) { oTarget.addEventListener(sEventType, fnHandler, false); } else if (oTarget.attachEvent) { oTarget.attachEvent("on" + sEventType, fnHandler); } else { oTarget["on" + sEventType] = fnHandler; } }; var Class = { create: function() { return function() { this.initialize.apply(this, arguments); } } } var Extend = function(destination, source) { for (var property in source) { destination[property] = source[property]; } return destination; } var DateSelector = Class.create(); DateSelector.prototype = { initialize: function(oYear, oMonth, oDay, options) { this.SelYear = $(oYear);//年选择对象 this.SelMonth = $(oMonth);//月选择对象 this.SelDay = $(oDay);//日选择对象 this.SetOptions(options); var dt = new Date(), iMonth = parseInt(this.options.Month), iDay = parseInt(this.options.Day),
iMinYear = parseInt(this.options.MinYear), iMaxYear = parseInt(this.options.MaxYear); this.Year = parseInt(this.options.Year) || dt.getFullYear(); this.Month = 1 <= iMonth && iMonth <= 12 ? iMonth : dt.getMonth() + 1; this.Day = iDay > 0 ? iDay : dt.getDate(); this.MinYear = iMinYear && iMinYear < this.Year ? iMinYear : this.Year; this.MaxYear = iMaxYear && iMaxYear > this.Year ? iMaxYear : this.Year; this.onChange = this.options.onChange; //年设置 this.SetSelect(this.SelYear, this.MinYear, this.MaxYear - this.MinYear + 1, this.Year - this.MinYear); //月设置 this.SetSelect(this.SelMonth, 1, 12, this.Month - 1); //日设置 this.SetDay(); var oThis = this; //日期改变事件 addEventHandler(this.SelYear, "change", function(){ oThis.Year = oThis.SelYear.value; oThis.SetDay(); oThis.onChange(); }); addEventHandler(this.SelMonth, "change", function(){ oThis.Month = oThis.SelMonth.value; oThis.SetDay(); oThis.onChange(); }); addEventHandler(this.SelDay, "change", function(){ oThis.Day = oThis.SelDay.value; oThis.onChange(); }); }, //设置默认属性 SetOptions: function(options) { this.options = {//默认值 Year: 0,//年 Month: 0,//月 Day: 0,//日 MinYear: 0,//最小年份 MaxYear: 0,//最大年份 onChange: function(){}//日期改变时执行 }; Extend(this.options, options || {}); }, //日设置 SetDay: function() { //取得月份天数 var daysInMonth = new Date(this.Year, this.Month, 0).getDate(); if (this.Day > daysInMonth) { this.Day = daysInMonth; }; this.SetSelect(this.SelDay, 1, daysInMonth, this.Day - 1); }, //select设置 SetSelect: function(oSelect, iStart, iLength, iIndex) { //添加option oSelect.options.length = iLength; for (var i = 0; i < iLength; i++) { oSelect.options[i].text = oSelect.options[i].value = iStart + i; } //设置选中项 oSelect.selectedIndex = iIndex; } }; </script> </head> <body> <select id="idYear"></select> <select id="idMonth"></select> <select id="idDay"></select> <br /> 你选择的日期:<span id="idShow"></span> <script> var ds = new DateSelector("idYear", "idMonth", "idDay", { MaxYear: new Date().getFullYear() + 2, onChange: function(){ $("idShow").innerHTML = this.Year + "/" + this.Month + "/" + this.Day; } }); ds.onChange(); </script> </body> </html>