How to Detect a File Format and Check if the File is Encrypted with JavaScript via C++
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Sometimes you need to detect a file’s format before opening it because the file extension does not guarantee that the file content is appropriate. The file might be encrypted (a password-protected file) so it can’t be read directly, or we should not read it. Aspose.Cells for JavaScript via C++ provides the FileFormatUtil.detectFileFormat(Uint8Array) static method and some relevant APIs that you can use to process documents.
The following sample code illustrates how to detect a file format (using the file path) and check its extension. You can also determine whether the file is encrypted.
<!DOCTYPE html>
<html>
<head>
<title>Aspose.Cells Example</title>
</head>
<body>
<h1>Aspose.Cells File Format Detection Example</h1>
<input type="file" id="fileInput" accept=".xls,.xlsx,.csv" />
<button id="runExample">Run Example</button>
<a id="downloadLink" style="display: none;">Download Result</a>
<div id="result"></div>
</body>
<script src="aspose.cells.js.min.js"></script>
<script type="text/javascript">
const { Workbook, SaveFormat, Worksheet, Cell, Utils } = AsposeCells;
AsposeCells.onReady({
license: "/lic/aspose.cells.enc",
fontPath: "/fonts/",
fontList: [
"arial.ttf",
"NotoSansSC-Regular.ttf"
]
}).then(() => {
console.log("Aspose.Cells initialized");
});
document.getElementById('runExample').addEventListener('click', async () => {
const fileInput = document.getElementById('fileInput');
const resultDiv = document.getElementById('result');
if (!fileInput.files.length) {
resultDiv.innerHTML = '<p style="color: red;">Please select an Excel file.</p>';
return;
}
const file = fileInput.files[0];
const arrayBuffer = await file.arrayBuffer();
// Detect file format
const info = AsposeCells.FileFormatUtil.detectFileFormat(new Uint8Array(arrayBuffer));
// Gets the detected load format (converted getter -> property)
const extension = AsposeCells.FileFormatUtil.loadFormatToExtension(info.loadFormat);
const encrypted = info.isEncrypted;
console.log("The spreadsheet format is: " + extension);
console.log("The file is encrypted: " + encrypted);
resultDiv.innerHTML = `<p>The spreadsheet format is: <strong>${extension}</strong></p>
<p>The file is encrypted: <strong>${encrypted}</strong></p>`;
});
</script>
</html>