How Can JavaScript Access and Process Local Files?

Accessing Local Disk Files in JavaScript

In web development, opening local files presents security challenges that prevent direct access via methods like window.open(). However, there are alternative approaches that allow JavaScript to read and process local data.

FileReader API

The FileReader API provides a way to read files asynchronously. Here's an example:

function readSingleFile(e) {
  var file = e.target.files[0];
  if (!file) {
    return;
  }
  var reader = new FileReader();
  reader.onload = function(e) {
    var contents = e.target.result;
    displayContents(contents);
  };
  reader.readAsText(file);
}

In this example, a listener is attached to a <input type="file"> element. When a file is selected, the readSingleFile function is triggered, using FileReader.readAsText() to read the file as plain text. The result of the operation is passed to the displayContents function for display.

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