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How To Read Text File In Javascript

Reading text files in JavaScript is a useful skill, especially when working on web development projects that involve handling text data. In this article, we will walk you through the process of reading a text file in JavaScript step by step.

To read a text file in JavaScript, you need to use the FileReader object, which provides methods for reading files asynchronously. First, you need to create an input element of type file in your HTML document to allow users to select the text file they want to read:

Html

Next, you can add an event listener to the input element to capture the selected file when the user chooses a file:

Javascript

document.getElementById('fileInput').addEventListener('change', function() {
  const file = this.files[0];
  if (file) {
    readFile(file);
  }
});

In the above code snippet, we are getting the selected file from the input element and passing it to the `readFile` function, which we will define next.

Now, let's write the `readFile` function to read the contents of the selected text file:

Javascript

function readFile(file) {
  const reader = new FileReader();
  
  reader.onload = function(e) {
    const text = e.target.result;
    console.log(text);
    // Do something with the text content
  };

  reader.readAsText(file);
}

In the `readFile` function, we create a new `FileReader` object, set the `onload` event handler to handle the file reading operation, and finally use the `readAsText` method to read the file as plain text.

When the text file is successfully read, the `onload` event is triggered, and the content of the file is stored in the `result` attribute of the event. You can then access the text content and process it as needed. In the example above, we simply log the text content to the console, but you can perform any desired operations on the text data.

It's worth noting that reading files in JavaScript is subject to the same-origin policy, which restricts scripts hosted on different domains from interacting with each other. When reading files, ensure that the file is hosted on the same domain as your script to avoid security restrictions.

By following these simple steps and understanding the FileReader object in JavaScript, you can easily read text files and work with text data in your web applications. Experiment with the code examples provided here and explore additional functionalities offered by the FileReader API to enhance your file reading capabilities. Happy coding!

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