As shown in the figure, you can see from the code that the screenshot method is triggered by a stand-alone machine, but why is it triggered by double-click in reality?

<img  id="jp" src="../../../images/common/img/jt.png" onclick="catchScreen()"/>"


function catchScreen(){
    
    PrintScreen.BeginCatchScreen();
}

var PrintScreen = {
        BeginCatchScreen:function(){
            try{
                var catchScreen = document.getElementById("CatchScreen");
                if(catchScreen.getVersion()<1002){
                    Ext.Msg.alert("",",!!",function(val){
                        if(val=="ok"){
                            var isWnd = window.open("down.html","activex","");
                            isWnd.moveTo(0,0);
                            isWnd.focus();
                        }
                    });
                    return;
                } 
                //alert(serverName+serverPort+basepath);
                catchScreen.BeginCatchScreen(serverName,serverPort,basepath+"/fileUploadAction.do?functionType=catchscreen",1);
            }catch(e){
                Ext.Msg.alert("",",!!",function(val){
                    if(val=="ok"){
                        var isWnd = window.open("down.html","activex","");
                        isWnd.moveTo(0,0);
                        isWnd.focus();
                    }
                });
            }
            
        },
        showPrintScreen:function(){
            var catchScreen = Ext.getDom("CatchScreen");
            var filepath = catchScreen.GetFileName();
            //alert(filepath);
            var inputMsg =document.getElementById("message");
            var img = "<img width="210px" height="150px" ondblclick="screenDblclick(\""+filepath+"\")" src="../../../"+filepath+""  alt="screenimg">";
            //
        //    var inputMsgHtml = inputMsg.innerHTML;
            MsgNode.msg = filepath;
            inputMsg.innerHTML = img;
        },
        filterContent:function(content){
            var newContent = content;
            if(newContent.indexOf("screenimg")!=-1){
                filepath = newContent.split("=")[1];
                newContent = "<img class=\"catchScreenImg\" ondblclick="screenDblclick(\""+filepath+"\")" src="../"+filepath+""  alt="screenimg">";
            }
            for(var p in emotions){
                while(newContent.indexOf("[-sharp"+emotions[p].EMOCODE+"]")!=-1){        
                    newContent = newContent.replace("[-sharp"+emotions[p].EMOCODE+"]","<img src="images/emotion/"+emotions[p].SRC+"" />");
                }
            }
            return newContent;
        }
}

A strange problem can be seen from the code that when you click the "img" tag, the screenshot method is triggered, and the breakpoint aler goes the same way, but the actual situation is: click does not respond, only double-click can trigger the screenshot method, it feels very strange

your img tag does not define the ondblclick method. When you click the button and execute until the double-click event, you report an error, and the following code does not execute. So it won't alert.