How to save files using JavaScript

JavaScript is a programming language widely used in web development to interact with users through the browser. In many web applications, users need to save some data to their local computer so that it can be used again in future sessions. JavaScript does this by using a mechanism called file saving. In this article, we will learn how to save a file on your local computer using JavaScript.

Overview

Saving a file refers to storing data on your local computer's hard drive. This can be achieved by using the file saving mechanism in JavaScript. When the user clicks the save button, a new file is created on the local computer that contains user input or data from the application. It is commonly used in web applications such as video players, document editors, image editors, etc. to allow users to download and save edited files.

Saving files using the FileSaver.js library

FileSaver.js is a popular third-party JavaScript library that can be used to save files. It uses a Blob object in JavaScript to create a file containing data and saves it to the user's local computer by modifying the href property of the window.location object.

To use the FileSaver.js library, you need to do the following two steps:

Step 1 - Import the library

The following code demonstrates how to use a JavaScript file to introduce the FileSaver.js library :

<script src="https://cdn.jsdelivr.net/npm/file-saver@2.0.2/dist/FileSaver.min.js"></script>

Step 2 - Save the file using the saveAs() function in the library

The following code demonstrates how to save the file using the saveAs() function:

function saveFile() {
  var data = "Hello, World!";
  var filename = "hello.txt";
  var file = new Blob([data], {type: 'text/plain'});
  saveAs(file, filename);
}

In this example , we create a file called "hello.txt" and write the string "Hello, World!" into it. We then use the saveAs() function to pass it the Blob object and filename. During the file saving process, the user will see a file saving dialog box prompting the user to specify the location and file name of the file to be saved.

Saving files using FileReader and Blob objects

FileReader and Blob objects are native JavaScript APIs. Blob objects represent binary data and can be used to create files containing the data. FileReader can read the file and return a string variable, which can then be written to the user's local computer.

Step 1 - Create a Blob object and save it

The following code demonstrates how to create a Blob object and save it to a local file:

function saveFile() {
  var data = "Hello, World!";
  var filename = "hello.txt";
  var file = new Blob([data], {type: 'text/plain'});
  var a = document.createElement('a');
  a.href = window.URL.createObjectURL(file);
  a.download = filename;
  a.click();
}

Here, we create A file called "hello.txt" and writes the string "Hello, World!" into it. We create a URL containing a Blob object using the window.URL.createObjectURL() method. We then created a link and downloaded the file.

Step 2 - Write data to file

The following code demonstrates how to write input data to FileReader:

function saveFile() {
  var data = "Hello, World!";
  var filename = "hello.txt";
  var file = new Blob([data], {type: 'text/plain'});

  var reader = new FileReader();
  reader.onload = function(event) {
    var text = event.target.result;
    var a = document.createElement('a');
    a.href = 'data:text/plain;charset=utf-8,' + encodeURIComponent(text);
    a.download = filename;
    a.click();
  };
  reader.readAsText(file);
}

Here, we create a file named " hello.txt" file and write the string "Hello, World!" into it. We use the FileReader instance readAsText() method to read text from a file and return that text on success. With this text, we create a new link and download the file.

Conclusion

In this article, we discussed how to save a file on your local computer through JavaScript. The JavaScript file saving mechanism can be used in many web applications such as video players, document editors, image editors, etc. We demonstrated two different implementations using the FileSaver.js library and the native JavaScript API. These implementations are easy to use and provide a better user experience for web applications.

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