How to Create and Save text file in JavaScript

How to Create and Save text file in JavaScript

As we know that JavaScript is one of the most popular high-level, interpreted programming language in the world. Now it is capable to do almost everything that we are doing in other programming languages. To know more about check out the StackOverflow 2018 survey.

What we’ll build

In this tutorial, we will create and save the data into a text file. To do that we’ll write:

1. A JavaScript function that fire on the button click event.
2. Create a Blob constructor, pass the data in it to be to save and mention the type of data.
3. And finally, call the saveAs(Blob object, «your-file-name.text«) function of FileSaver.js library.

Note: To create and save data into a text file, I have used a third party FileSaver.js library.

Let’s jump into the actual juicy part of the code.

1. Saving static data

1.1 Create a function that executes on button click event.

function saveStaticDataToFile()

1.2 Instantiate the Blob object and pass a text string as the first parameter and blob type as the second parameter.

var blob = new Blob(["Welcome to Websparrow.org."], < type: "text/plain;charset=utf-8" >);

1.3 Now call the saveAs function which takes blob object as input and let you save files on web browser.

Check out the complete example.

         Click to Save  

2. Saving dynamic data

To save user input data into a text file, first, we need to store user’s data into a variable and pass that variable as Blob first parameter. Check out the complete code example.

          We love to share our experiments, ideas, and knowledge with everyone by writing articles on the latest technology trends. Click to Save  

Remember: Don’t forget to import FileSaver.js library in your document (html/jsp/etc).

References

Источник

How to Create and Save text file in JavaScript?

In this tutorial, we will learn to create and save the text file in JavaScript. Sometimes, developers need to get texts or content from the user and allow users to store content in a text file and allow the file to download to the local computer.

Many JavaScript libraries are available to achieve our goal, but we have used the best two libraries in this tutorial to create and save the text file.

Create a text file using custom text and save it to a local computer

We will use normal JavaScript operations to create and save the text file on the user’s computer. Users can use the HTML tag to create a text file from the custom content and save it.

Developers should follow the below syntax to create a text file from the text input and save it.

Syntax

In the above syntax, we have taken the content from the users, converted it to blog object, and then saved it to the text file.

Algorithm

Users should follow the below steps to understand the above syntax.

Example

We have written the code in the example below by following the syntax and algorithm. We have created the HTML . Users can enter the content they want to add to the file and click on the ‘save file’ button to save the text file on the computer.

When a user clicks on the ‘save file’ button, it will call the ‘downloadFile()’ function, in which we have added the code to create and save the text files.

html> body> h2> Create a text file and save it to a local computer using JavaScript. /h2> p> Enter the file content:- /p> textarea> /textarea> br/> button onclick = "downloadFile()"> save File /button> script> const downloadFile = () =>  const link = document.createElement("a"); const content = document.querySelector("textarea").value; const file = new Blob([content],  type: 'text/plain' >); link.href = URL.createObjectURL(file); link.download = "sample.txt"; link.click(); URL.revokeObjectURL(link.href); >; /script> /body> /html> 
 

Use the FileSaver JavaScript library to create and save the text file

The ‘FileSaver’ is the JavaScript library that we can use to create a text file in vanilla JavaScript. Users can use the CDN of the library to use it with HTML and JavaScript.

Users should use the below syntax to use the FileSaver library.

Syntax

// Create blob object with file content var blob = new Blob(["This is a sample file content."], < type: "text/plain;charset=utf-8", >); // Create and save the file using the FileWriter library saveAs(Content, fileName);

In the above syntax, we have used some text to create the blob object of the ‘text’ type. Also, we have used the ‘saveAs()’ function of the FileWriter library to create and save the text file.

Parameters

The ‘saveAs’ function takes two parameters.

• Content − It is the content that needs to be stored in the file.
• filename − It is a default file name when a user downloads it.

Example

We have added the CDN of the ‘FileWriter’ library in the section of the below code. When a user clicks on the ‘create text file’ button, it will invoke the ‘CreateTextFile()’ function in JavaScript, which creates the blob object of the sentence ‘This is a simple file content’ and executes the ‘saveAs()’’function to save the text file.

html> head> script src = "https://cdnjs.cloudflare.com/ajax/libs/FileSaver.js/2.0.0/FileSaver.min.js" integrity="sha512-csNcFYJniKjJxRWRV1R7fvnXrycHP6qDR21mgz1ZP55xY5d+aHLfo9/FcGDQLfn2IfngbAHd8LdfsagcCqgTcQ= token operator">= "anonymous" referrerpolicy = "no-referrer"> /script> /head> body> h2>Create text file and save it to local computer using i> FileSaver /i> JavaScript Library./h2> button type = "button" onclick = "CreateTextFile();">Create Text File/button> script> function CreateTextFile()  var blob = new Blob(["This is a sample file content."],  type: "text/plain;charset=utf-8", >); saveAs(blob, "download.txt"); > /script> /body> /html> 
 

Save the content of the image in a text file using the FileSaver JavaScript library

In this section, we have used the same library, ‘FileSaver’, but rather than storing the normal texts to the file, we string the image after converting the image to a blob object.

Users can follow the syntax below to store the image in the text file format and save it.

Syntax

// Access the file input by Id var element = document.getElementById("uploadedImage"); // Add onchange event to file input element.onchange = function (event) < // Convert image content to text var blob = new Blob[event.target.files[0]], < type: "text/plain;charset=utf-8", >); // Create text file using image’s content and save it saveAs(blob, "download.txt"); >;

In the above syntax, we take the file the user uploads into the HTML and convert its content to a blob object. After that, we create the text file using the blob object and save the file to the local computer.

Example

We have used the ‘FileSaver’ JavaScript library in the example below, as shown in the above syntax. We have created the file input field, allowing users only to upload the image file.

In JavaScript, we have added the event listener to the file input, and as the user uploads a file, it will create a text file using the uploaded image file and save it to the user’s computer.

html> head> script src = "https://cdnjs.cloudflare.com/ajax/libs/FileSaver.js/2.0.0/FileSaver.min.js" integrity = "sha512-csNcFYJniKjJxRWRV1R7fvnXrycHP6qDR21mgz1ZP55xY5d+aHLfo9/FcGDQLfn2IfngbAHd8LdfsagcCqgTcQ= token operator">= "anonymous" referrerpolicy = "no-referrer"> /script> /head> body> h2>Upload image and add its content to text file and save it to computerusing i> FileSaver /i> JavaScript Library./h2> input type = "file" id = "uploadedImage" accept = "image/png, image/gif, image/jpeg"/> script> var element = document.getElementById("uploadedImage"); element.onchange = function (event)  var blob = new Blob[event.target.files[0]],  type: "text/plain;charset=utf-8", >); saveAs(blob, "download.txt"); >; /script> /body> /html> 
 

Источник

File: File() constructor

The File() constructor creates a new File object instance.

Syntax

new File(bits, name) new File(bits, name, options) 

Parameters

An iterable object such as an Array , having ArrayBuffer s, TypedArray s, DataView s, Blob s, strings, or a mix of any of such elements, that will be put inside the File . Note that strings here are encoded as UTF-8, unlike the usual JavaScript UTF-16 strings.

A string representing the file name or the path to the file.

An options object containing optional attributes for the file. Available options are as follows:

A string representing the MIME type of the content that will be put into the file. Defaults to a value of «» .

A number representing the number of milliseconds between the Unix time epoch and when the file was last modified. Defaults to a value of Date.now() .

Examples

const file = new File(["foo"], "foo.txt",  type: "text/plain", >); 

Specifications

Browser compatibility

BCD tables only load in the browser

See also

Found a content problem with this page?

This page was last modified on Apr 7, 2023 by MDN contributors.

Your blueprint for a better internet.

MDN

Support

Our communities

Developers

Visit Mozilla Corporation’s not-for-profit parent, the Mozilla Foundation.
Portions of this content are ©1998– 2023 by individual mozilla.org contributors. Content available under a Creative Commons license.

Источник