USB 條碼掃描器無需服務器調用即可重復掃描

Question

不確定我的術語在所有這些方面是否正確。 我知道我的代碼也沒有效率。 在這一點上尋找功能而不是效率。 （只是一個試圖解決后勤問題的老師）。

我有一個 web 應用程序，我們用來檢查學生進出圖書館。 由於新型冠狀病毒肺炎，我們正在嘗試減少觸摸鍵盤並加快辦理登機手續。 為此，我們有一個 USB 掃描儀可以掃描學生證。

我的 Webapp 加載模板 html，然后將名稱等添加到不同的選擇元素。 當學生簽到時，姓名會出現在窗口的另一半，並等待他們單擊其姓名旁邊的結帳。 我相信這是在所謂的客戶端完成的。

為了添加條形碼掃描儀，我添加了一個帶有文本輸入的表單元素。 這是讓條碼掃描器與客戶端交互的唯一方法嗎？

<form><input type="text" id = "barcodeInput" size="1"></form>  

然后我有一些 jQuery 測試以查看輸入是條形碼（按下前綴和返回鍵），如果是這樣，則條形碼中的學生 ID 號將通過循環以在學生的選擇選項中找到匹配的 ID姓名（ID 存儲在值中，學生姓名存儲在文本中）。 此處也阻止了默認操作

所有這些都有效，我可以讓 1 個學生添加到我的應用程序的“簽入”面板中。

我無法讓掃描儀在第二個學生身上工作。 我認為這與我使用表單輸入元素的事實有關，這可能需要服務器調用，但我不能這樣做，因為我需要有越來越多的學生被簽入圖書館。

我借了這個，目前正在使用

$(document).ready(function() {
    var barcode=""; //sets my variable
    $(document).keydown(function(e) //looking to intercept the barcode scanner output
    {
        var code = (e.keyCode ? e.keyCode : e.which); //don't really know what this does since I borrowed this
        if(code==13&&(barcode.substring(1,5)=="SCAN"))// Enter key hit & from scanner
        {
            e.preventDefault(); //stops the enter key from actually "running" and stops the barcode from going into the input field (I think)
            barcode = barcode.slice(5);// remove the prefix so I am left with student number aka barcode
            alert(barcode); //lets me know I'm getting the correct student number
            processBarcode(barcode);        //sends to process barcode
        }
        else if(code==9)// Tab key hit    //I may not need these next 10ish lines
        {
            e.preventDefault();
            alert(barcode);      
        }
        else
        {
            e.preventDefault();
            barcode=barcode+String.fromCharCode(code);
        }
    });
});

這會在 select 元素中找到學生，然后更改 select 元素以讀取該姓名，並將姓名發布在“誰正在簽入”表格單元格中

function processBarcode(barcode){
     var name = "";
   $("#studentNameSelect option").each(function(){ //runs through the select element that has all student names...the name is in the parameter "text" and student ID # is in the parameter val
        if($(this).val()==barcode){ //looking to see if the student ID # matches the specific option in the select element
             name = $(this).text(); //figure out the student name based on ID #
             $(this).prop('selected', true); //set the select element to show this specific option
             $("#selectedName").html(name);  //puts student name in a table cell so they know they are picking the correct name
             //$("#barcodeInput").trigger("reset"); //here I'm trying to get the form element input to reset so I can use it again...this didn't work so its commented out
             $("#teacherNameSelect").focus(); //puts the focus onto the next select item so I can do other things
             return false; //breaks the each loop once student name has been found
        }
    }); 
}

然后這是將姓名移動到“已登記”面板上的代碼，以便下一個學生可以登記

function buildAttendanceRow(stringPackage){ //this function takes info from the selection panel and builds a table row in the "I'm at the library" panel. Students click check out when they leave the library
console.log(stringPackage);
    var package = JSON.parse(stringPackage); //receives a package of info from the selects, I do send this to a server function to email teachers that student arrived to the library...
console.log(package);
    var html = "";
    var hiddenId = new Date().getTime().toString(); //this cell is used to keep track of a specific instance of a student checked into the library so I can remove later and then mark in a backend spreadsheet database
    var nameCell = '<td class="package" id="'+hiddenId+'">'+package.student+'</td>';
    var checkOutButton = '<input type="button" value="Check Out" id="COButton">';
    var checkoutButtonCell = '<td class="center">'+checkOutButton+'</td>';
    html+="<tr>"+nameCell+checkoutButtonCell+"</tr>";
    $("#checkedInTable").append(html);   //puts the new table row into the checked in table
    $('#'+hiddenId).data("package",package); //stores info so I can remove table row and update database
    
    
    var lastTableRow = $('#checkedInTable tr:last');
    var button = lastTableRow.find('#COButton');
        //add the click function for removing row and sending checked out info to server for email and for database purposes
        button.click(function(e){
            var x = e.pageX;
            var y = e.pageY;
            var o = {
                left: x,
                top: y
            };
           $("#progressMonitor").show().offset(o);
            $(this).prop("disabled",true);
            var row = $(this).closest('tr');
            var carrierCell =$('#'+hiddenId); 
            var d = new Date();
            var payload = new Object(); //this object gets transferred to the server function, the user interface doesn't refresh here, it just has a dynamic html table built and shrunk as kids check in or check out
                payload.checkInTime = carrierCell.data("package").checkInTime;
                payload.timeIn = carrierCell.data("package").timeIn;
                payload.student = carrierCell.data("package").student;
                payload.teacherEmail = carrierCell.data("package").teacherEmail;
                payload.teacherName = carrierCell.data("package").teacherName;
                payload.reason = carrierCell.data("package").reason;
                payload.checkOutTime = d;
                payload.timeOut = d.getTime();
           var stringPayload = JSON.stringify(payload);
           row.hide();
           alternateRowColors($("#checkedInTable"));
           google.script.run.withSuccessHandler(emailAndRecordsSuccess).withFailureHandler(emailAndRecordsFailure).emailAndRecords(stringPayload);//calling the server function
        });
    
    var numRows =  $("#checkedInTable tr" ).length;
    if(numRows>2){
        alphaSortTable(); //puts the student names in alpha order so it is easier for them to checkout of the library
    }
    alternateRowColors($("#checkedInTable")); 
    $("#progressMonitor").hide();
    $("#barcodeInput").focus(); //here is me trying to get the scanner back into the input field so there is somewhere for the scanner data to go; I expected this to be all I needed to do, but at this point, even though the input is focused, the the scanner won't fire onto the document or into the field or anything like that
     alert($("#barcodeInput").val()); //this is telling me that there is no value in the input field at this point, I thought there might be info stored here screwing up the scanner

}

Answer 1

解決方案是在我的客戶端工作完成后將一個函數重新綁定到文檔。 將其更改為命名函數：

$(document).ready(function() {
    var barcode=""; 
    $(document).keydown(function(e) 
    {
        var code = (e.keyCode ? e.keyCode : e.which); 
        if(code==13&&(barcode.substring(1,5)=="SCAN"))
        {
            e.preventDefault(); 
            barcode = barcode.slice(5);
            processBarcode(barcode); 
        }else if(code==9)// Tab key hit  
             {e.preventDefault();     
        }else{
            e.preventDefault();
            barcode=barcode+String.fromCharCode(code);
        }
    });
});

我現在有：

function getBarcode(){
var barcode=""; 
    $(document).keydown(function(e) 
    {
        var code = (e.keyCode ? e.keyCode : e.which); 
        if(code==13&&(barcode.substring(1,5)=="SCAN"))
        {
            e.preventDefault(); 
            barcode = barcode.slice(5);
            processBarcode(barcode); 
        }else if(code==9)// Tab key hit  
             {e.preventDefault();     
        }else{
            e.preventDefault();
            barcode=barcode+String.fromCharCode(code);
        }
    });

和

$(document).ready(function() {
     getBarcode();
}

我可以打電話

getBarcode();

任何地方重新連接要尋找條碼掃描儀的文件。