<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML>
<HEAD>
<TITLE> test command </TITLE>
<META NAME="Author" CONTENT="emu">
<SCRIPT LANGUAGE="JavaScript">
<!--
var actionStack = [];//操作栈
var actionIndex = 0;//操作栈中当前操作的指针
//----------------------- command对象基类 ------------------------------
function BaseAction(){
}
BaseAction.prototype.exec=function(){
actionStack[actionIndex++] = this;
actionStack.length = actionIndex;
}
BaseAction.prototype.undo=function(){
alert("此操作未定义相应的undo操作");
}
BaseAction.prototype.redo=function(){
alert("此操作未定义相应的redo操作");
}
//----------------------- change操作的command对象 ------------------------------
function ChangeAction(elm){
this.sourceElement = elm;
this.oldValue = elm.defaultValue;
this.newValue = elm.value;
elm.defaultValue = elm.value;
this.status = "done";
}
ChangeAction.prototype = new BaseAction();
ChangeAction.prototype.undo = function(){
if (this.status != "done") return;
this.sourceElement.value = this.sourceElement.defaultValue = this.oldValue;
this.status = "undone";
}
ChangeAction.prototype.redo = function(){
if (this.status != "undone") return;
this.sourceElement.value = this.newValue;
this.status = "done";
}
//--------------------- 全局函数 ----------------------------
function undo(){
if (actionIndex>0){
actionStack[--actionIndex].undo();
}
}
function redo(){
if (actionIndex<actionStack.length){
actionStack[actionIndex++].redo();
}
}
function changeValue(event){
event = (event) ? event:window.event;
new ChangeAction(event.srcElement || event.target).exec();
}
//-->
</SCRIPT>
</HEAD>
<BODY oncontextmenu="return false">
<input type=button onclick=undo() value=undo>
<input type=button onclick=redo() value=redo>
<input value="drag me" onchange="changeValue(event)" style="position:absolute;left:150px;color:blue">
<input value="drag me" onchange="changeValue(event)" style="position:absolute;left:350px;color:green">
<input value="drag me" onchange="changeValue(event)" style="position:absolute;left:550px;color:violet">
</BODY>
</HTML>
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