JavaScript: how to read a CSV file with the FileReader object

JavaScript: how to read a CSV file with the FileReader object

Reading a CSV file with JavaScript can be done using the FileReader object, which allows you to read the contents of a file as a string or byte array.

Reading a CSV file with JavaScript can be done using the FileReader object, which allows you to read the contents of a file as a string or byte array. The CSV file, which contains comma-separated data, can then be processed and manipulated by JavaScript.

To get started, you need to instantiate the FileReader object:


const reader = new FileReader();

Next, you can use the readAsText() method to read the file contents as a string:


reader.readAsText(file);

In this case, file represents the File object selected by the user via the HTML file input.

Once the file reading is complete, the contents of the CSV file can be accessed using the result property of the FileReader object:


reader.onload = () => {
  const csvContent = reader.result;
  // Perform operations on the contents of the CSV file
};

The content of the CSV file can then be manipulated, for example by splitting the rows and columns using the split() method and creating an array of objects representing the data.

In general, using the FileReader object to read CSV files in JavaScript is a simple and effective way to manipulate tabular data and integrate it in your code.