Uncaught Typeerror Failed To Execute Readasdataurl On Filereader Parameter 1 Is Not Of Type Blob

Have you ever encountered the frustrating error message "Uncaught TypeError: Failed to execute 'readAsDataURL' on 'FileReader': parameter 1 is not of type 'Blob'" while working with File API in JavaScript? Don't worry, you're not alone! This error can be confusing at first, but with a little guidance, you'll be able to resolve it quickly.

This error typically occurs when you try to use the FileReader object to read data from a file that is not in Blob format. Blob is a data type in JavaScript that represents raw data, usually in the form of file data. When you pass a parameter that is not a Blob to the readAsDataURL method, JavaScript throws this error.

To fix this issue, you need to ensure that the parameter you pass to readAsDataURL is indeed a Blob object. To convert a file into a Blob object, you can use the File constructor (which inherits from Blob) or the Blob constructor itself.

Here's a simple example demonstrating how to load a file as a Blob using the File constructor:

const input = document.getElementById('file-input');
input.addEventListener('change', function() {
  const file = input.files[0];
  
  if (file) {
    const reader = new FileReader();
    
    reader.onload = function(e) {
      const dataURL = e.target.result;
      // Do something with the data URL
    };
    
    reader.readAsDataURL(file);
  }
});

In this code snippet, we first get a reference to the file input element. We then listen for the 'change' event on the input and retrieve the selected file. Next, we create a new instance of FileReader and set up an event handler for the 'load' event, where we can access the data URL generated by the FileReader.

By following this pattern and ensuring that the parameter passed to readAsDataURL is a Blob object, you can avoid encountering the "Uncaught TypeError: Failed to execute 'readAsDataURL' on 'FileReader': parameter 1 is not of type 'Blob'" error.

Remember, handling file inputs and reading file data in JavaScript can sometimes be tricky, but with a clear understanding of data types and proper usage of FileReader methods, you can navigate these challenges successfully.

Next time you come across this error, don't panic! Take a moment to review your code, double-check the data type you're passing to FileReader, and make the necessary adjustments to resolve the issue. Happy coding!