使用AngularJS如何检查文件夹中是否存在PDF文件? [英] Using AngularJS how to check a PDF file exist in a folder or not?
问题描述
我有一个学生名单.
对于某些学生，我必须显示一个链接，单击此链接后，他们的进度卡应该会加载(这是一个.pdf文件).对于其他用户，不应显示该链接.
I have a list of students.
For some students I have to show a link, and on clicking this link their progress card should load (it is a .pdf file). For others, the link should not be shown.
我是通过给他们的进度卡提供相同的学生ID来完成的，如果是这个特定学生，则显示链接；否则，请勿显示链接.我只能以这种方式为5或6个学生做这件事.我不能为1000名学生做到这一点.
I have done this by giving the same student id to their progress card and if it is this particular student then show the link; otherwise, don't show the link. I can do it this way for only 5 or 6 students. I cant do this for 1000 students.
以下是我的AngularJS代码:
The following is my AngularJS code:
if (response.student_id == 'SD0001' || response.student_id == 'SD0002' || response.student_id == 'SD0004') {
$scope.pdfData = true;
$scope.StudentPDFFile = response.student_id+'.pdf';
} else {
$scope.pdfData = false;
}
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.6.6/angular.min.js"></script>
<body id="ng-app" ng-app>
<div ng-switch on="pdfData">
<div ng-switch-when="false"></div>
<div ng-switch-when="true">
<span class="font-10">Download Performance Report</span>
<a href="http://www.example.com/s-pdf/{{StudentPDFFile}}" target="_blank"> click here</a>
</div>
</div>
</body>
这里我还没有指定控制器，这是骨架功能正在为我工作.
Here I haven't specified the controller, this is skeleton functionality is working for me.
对于1000条记录，我该怎么做?
For 1000 records how I can do this?
推荐答案
只要您与pdf文件位于同一个域中，就可以发出http请求来确定文件是否存在.
You can make a http request to determine if the file exists as long as you are on the same domain as the pdf file.
对于给定的学生证(在您的代码中为response.student_id)，它看起来像这样:
For a given student ID (which in your code appears to be response.student_id) it looks like this:
if(response.student_id) {
var url = 'http://www.example.com/s-pdf/' + response.student_id + '.pdf';
var request = new XMLHttpRequest();
request.open('HEAD', url, false);
request.send();
if(request.status == 200) {
$scope.pdfData = true;
$scope.StudentPDFFile = response.student_id+'.pdf';
} else {
$scope.pdfData = false;
}
} else {
$scope.pdfData = false;
}
'HEAD'是确保文件存在所需的全部内容.您也可以使用'GET'，但在这种情况下似乎不需要整个文件.
The 'HEAD' is all that is necessary to ensure that the file exists; you could also use 'GET' but it doesn't seem like you need the whole file in this situation.
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