亚洲国产日韩欧美一区二区三区,精品亚洲国产成人av在线,国产99视频精品免视看7,99国产精品久久久久久久成人热,欧美日韩亚洲国产综合乱

Table of Contents
What can you do with a Blob?
How to create a Blob
How to read or use a Blob
Home Web Front-end JS Tutorial What is the Blob object in JavaScript?

What is the Blob object in JavaScript?

Jun 22, 2025 am 12:41 AM

Blob objects are used to process immutable raw data in the browser and are often used for binary data operations such as files and pictures. 1. You can create downloadable files; 2. Read content through FileReader; 3. Upload files through FormData; 4. Create the object URL to display the picture directly. Each blob contains size and type attributes. The creation method is new Blob(dataArray, {type}), which can combine multiple segments of data. The ways to read or use a blob include: 1. URL.createObjectURL() generates a URL; 2. FileReader reads the content; 3. Send to the server through fetch. Blob itself has simple functions, but it has become the core tool for processing files with other APIs.

What is the Blob object in JavaScript?

The Blob object in JavaScript is a built-in data structure that represents immutable raw data. It's often used to handle binary data such as files, images, audio, or video in the browser. You might encounter Blobs when working with file uploads, downloading content from APIs, or manipulating media.


What can you do with a Blob?

A Blob gives you a way to work with chunks of data without needing to load everything into memory at once. Here are some common uses:

  • Create downloadable files on the fly
  • Read and manipulate file content using FileReader
  • Upload files through FormData and fetch
  • Display images directly in the browser by creating an object URL

Each Blob has a .size (in bytes) and a .type (like image/png or text/plain ), which helps you understand what kind of data it contains.


How to create a Blob

Creating a Blob is straightforward. You pass it an array of data and optionally a type:

 const text = 'Hello, world!';
const blob = new blob([text], { type: 'text/plain' });

You can also combine multiple pieces of data:

 const data1 = 'Part one';
const data2 = new Uint8Array([72, 101, 108, 108, 111]); // "Hello" in ASCII
const blob = new Blob([data1, data2], { type: 'text/plain' });

If you want to see the contents of a Blob, you'll need to use a FileReader or convert it into a URL.


How to read or use a Blob

Since Blobs hold raw data, you usually need to process them before displaying or sending them somewhere. Here are a few typical approaches:

  • Convert to a URL : Use URL.createObjectURL(blob) to display images or let users download files.

     const url = URL.createObjectURL(blob);
    const a = document.createElement('a');
    a.href = url;
    a.download = 'hello.txt';
    a.click();
  • Read contents with FileReader : Useful for inspecting or modifying data.

     const reader = new FileReader();
    reader.onload = function(event) {
      console.log(event.target.result); // The content as a string
    };
    reader.readAsText(blob);
  • Send via fetch : Append to FormData or send directly in a POST request.

     const formData = new FormData();
    formData.append('file', blob, 'filename.txt');
    
    fetch('/upload-endpoint', {
      method: 'POST',
      body: formData
    });

    These methods make Blobs flexible for both client-side processing and communication with servers.


    Basically, the Blob object is a simple but powerful tool for handling binary data in web applications. It doesn't do much on its own, but paired with other APIs like FileReader, URL, or fetch, it becomes essential for many file-related tasks.

    The above is the detailed content of What is the Blob object in JavaScript?. For more information, please follow other related articles on the PHP Chinese website!

Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undress AI Tool

Undress AI Tool

Undress images for free

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Clothoff.io

Clothoff.io

AI clothes remover

Video Face Swap

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Tools

Notepad++7.3.1

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

Hot Topics

PHP Tutorial
1488
72
How to make an HTTP request in Node.js? How to make an HTTP request in Node.js? Jul 13, 2025 am 02:18 AM

There are three common ways to initiate HTTP requests in Node.js: use built-in modules, axios, and node-fetch. 1. Use the built-in http/https module without dependencies, which is suitable for basic scenarios, but requires manual processing of data stitching and error monitoring, such as using https.get() to obtain data or send POST requests through .write(); 2.axios is a third-party library based on Promise. It has concise syntax and powerful functions, supports async/await, automatic JSON conversion, interceptor, etc. It is recommended to simplify asynchronous request operations; 3.node-fetch provides a style similar to browser fetch, based on Promise and simple syntax

React vs Angular vs Vue: which js framework is best? React vs Angular vs Vue: which js framework is best? Jul 05, 2025 am 02:24 AM

Which JavaScript framework is the best choice? The answer is to choose the most suitable one according to your needs. 1.React is flexible and free, suitable for medium and large projects that require high customization and team architecture capabilities; 2. Angular provides complete solutions, suitable for enterprise-level applications and long-term maintenance; 3. Vue is easy to use, suitable for small and medium-sized projects or rapid development. In addition, whether there is an existing technology stack, team size, project life cycle and whether SSR is needed are also important factors in choosing a framework. In short, there is no absolutely the best framework, the best choice is the one that suits your needs.

JavaScript Data Types: Primitive vs Reference JavaScript Data Types: Primitive vs Reference Jul 13, 2025 am 02:43 AM

JavaScript data types are divided into primitive types and reference types. Primitive types include string, number, boolean, null, undefined, and symbol. The values are immutable and copies are copied when assigning values, so they do not affect each other; reference types such as objects, arrays and functions store memory addresses, and variables pointing to the same object will affect each other. Typeof and instanceof can be used to determine types, but pay attention to the historical issues of typeofnull. Understanding these two types of differences can help write more stable and reliable code.

JavaScript time object, someone builds an eactexe, faster website on Google Chrome, etc. JavaScript time object, someone builds an eactexe, faster website on Google Chrome, etc. Jul 08, 2025 pm 02:27 PM

Hello, JavaScript developers! Welcome to this week's JavaScript news! This week we will focus on: Oracle's trademark dispute with Deno, new JavaScript time objects are supported by browsers, Google Chrome updates, and some powerful developer tools. Let's get started! Oracle's trademark dispute with Deno Oracle's attempt to register a "JavaScript" trademark has caused controversy. Ryan Dahl, the creator of Node.js and Deno, has filed a petition to cancel the trademark, and he believes that JavaScript is an open standard and should not be used by Oracle

Handling Promises: Chaining, Error Handling, and Promise Combinators in JavaScript Handling Promises: Chaining, Error Handling, and Promise Combinators in JavaScript Jul 08, 2025 am 02:40 AM

Promise is the core mechanism for handling asynchronous operations in JavaScript. Understanding chain calls, error handling and combiners is the key to mastering their applications. 1. The chain call returns a new Promise through .then() to realize asynchronous process concatenation. Each .then() receives the previous result and can return a value or a Promise; 2. Error handling should use .catch() to catch exceptions to avoid silent failures, and can return the default value in catch to continue the process; 3. Combinators such as Promise.all() (successfully successful only after all success), Promise.race() (the first completion is returned) and Promise.allSettled() (waiting for all completions)

What is the cache API and how is it used with Service Workers? What is the cache API and how is it used with Service Workers? Jul 08, 2025 am 02:43 AM

CacheAPI is a tool provided by the browser to cache network requests, which is often used in conjunction with ServiceWorker to improve website performance and offline experience. 1. It allows developers to manually store resources such as scripts, style sheets, pictures, etc.; 2. It can match cache responses according to requests; 3. It supports deleting specific caches or clearing the entire cache; 4. It can implement cache priority or network priority strategies through ServiceWorker listening to fetch events; 5. It is often used for offline support, speed up repeated access speed, preloading key resources and background update content; 6. When using it, you need to pay attention to cache version control, storage restrictions and the difference from HTTP caching mechanism.

Leveraging Array.prototype Methods for Data Manipulation in JavaScript Leveraging Array.prototype Methods for Data Manipulation in JavaScript Jul 06, 2025 am 02:36 AM

JavaScript array built-in methods such as .map(), .filter() and .reduce() can simplify data processing; 1) .map() is used to convert elements one to one to generate new arrays; 2) .filter() is used to filter elements by condition; 3) .reduce() is used to aggregate data as a single value; misuse should be avoided when used, resulting in side effects or performance problems.

JS roundup: a deep dive into the JavaScript event loop JS roundup: a deep dive into the JavaScript event loop Jul 08, 2025 am 02:24 AM

JavaScript's event loop manages asynchronous operations by coordinating call stacks, WebAPIs, and task queues. 1. The call stack executes synchronous code, and when encountering asynchronous tasks, it is handed over to WebAPI for processing; 2. After the WebAPI completes the task in the background, it puts the callback into the corresponding queue (macro task or micro task); 3. The event loop checks whether the call stack is empty. If it is empty, the callback is taken out from the queue and pushed into the call stack for execution; 4. Micro tasks (such as Promise.then) take precedence over macro tasks (such as setTimeout); 5. Understanding the event loop helps to avoid blocking the main thread and optimize the code execution order.

See all articles