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Handle file download from Ajax POST

I have a JavaScript application that sends an Ajax POST requests to a certain URL. The response might be a JSON string, or it might be a file (as an attachment). I can easily detect Content-Type and Content-Disposition in my Ajax call, but once I detect that the response contains a file, how do I offer the client to download it? I've read a number of similar questions here, but none of them provide the answer I'm looking for.

Please, please, please do not post answers suggesting that I shouldn't use Ajax for this, or that I should redirect the browser, because none of those is an option. Using a plain HTML form is also not an option. What I do need is to show a download dialog to the client. Can this be done and how?

Answer*

This worked for me.

```lang-html
<script>
    $(document).ready(function() {
        $(".download-button").click(function() {
            var val1 = $(this).data("column1");
            var val2 = $(this).data("column2");
            var val3 = $("#SearchString").val();
            var val4 = $(this).closest("tr").find(".textbox").val();

            $.ajax({
                url: '/TestDownload/DownloadFile',
                type: 'POST',
                data: {
                    val1: val1,
                    val2: val2,
                    val3: val3,
                    val4: val4
                },
                success: function (data, status, xhr) {
                    var contentDisposition = xhr.getResponseHeader('content-disposition');
                    var fileName = '';
                    if (contentDisposition && contentDisposition.indexOf('attachment') != -1) {
                        var startIndex = contentDisposition.indexOf('filename=') + 9;
                        var endIndex = contentDisposition.indexOf(';', startIndex);
                        if (endIndex === -1) {
                            endIndex = contentDisposition.length;
                        }
                        fileName = contentDisposition.substring(startIndex, endIndex);
                    }

                    var blob = new Blob([data], { type: 'application/octet-stream' });
                    var url = window.URL.createObjectURL(blob);
                    var a = document.createElement('a');
                    a.href = url;
                    a.download = fileName;
                    a.click();
                    window.URL.revokeObjectURL(url);
                    $("#errorMessage").text("File downloaded successfully.");
                },
                error: function(xhr, status, error) {
                    $("#errorMessage").text(xhr.responseText);
                }
            });
        });
    });
</script>
```

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– Community Bot

2023-09-27 01:20:21 +00:00
Commented Sep 27, 2023 at 1:20

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Handle file download from Ajax POST

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