


Trying to Disable CORS with Fetch and Dealing with 'Access-Control-Allow-Origin'
You've encountered a common challenge when attempting cross-origin requests from your client JavaScript code using Fetch. The error message you received indicates that the endpoint you're trying to fetch from doesn't include the 'Access-Control-Allow-Origin' header, which is required for cross-origin access.
Problem: You're attempting to use the object { mode: 'no-cors' } in Fetch to disable CORS, but this approach is incorrect.
Why 'no-cors' Mode Doesn't Work:
Setting mode: 'no-cors' in Fetch doesn't disable CORS; instead, it tells browsers to prevent your frontend JavaScript from accessing the response body and headers. This setting is usually not desirable, as you typically want your code to be able to access the response.
Solution: CORS Proxy
The solution to this problem lies in using a CORS proxy. A CORS proxy acts as an intermediary between your frontend code and the remote endpoint, enabling cross-origin requests by modifying response headers.
By using a CORS proxy, you can forward your requests through the proxy, which will add the necessary Access-Control-Allow-Origin header to the response. This allows your frontend code to access the response body and headers as if it were coming from the same origin.
Deploying Your Own Proxy
An easy way to deploy your own CORS proxy is to follow these steps:
- Clone the cors-anywhere GitHub repository (https://github.com/Rob--W/cors-anywhere).
- Install dependencies using npm install.
- Create a Heroku account and run heroku create.
- Push your code to Heroku using git push heroku master.
Once deployed, you'll have a running CORS proxy at a URL like https://cryptic-headland-94862.herokuapp.com.
Prefixing Your Request URL with the Proxy URL
To use the proxy, simply prefix your request URL with the proxy URL. For example, if you want to fetch https://example.com, you would use the following URL:
https://cryptic-headland-94862.herokuapp.com/https://example.com
By prefixing the request URL with the proxy, you'll be able to make cross-origin requests successfully, thanks to the Access-Control-Allow-Origin header added by the proxy.
Additional Considerations:
- Postman can access the endpoint because it's a debugging tool that ignores same-origin restrictions.
- Using mode: 'no-cors' or mode: 'opaque' in Fetch is not the correct approach to disabling CORS.
- CORS is a security measure, and it's important not to bypass it casually. Always consider the security implications before disabling CORS restrictions.
The above is the detailed content of How Can I Resolve Cross-Origin Request Errors When Fetching Data Using JavaScript?. For more information, please follow other related articles on the PHP Chinese website!

Detailed explanation of JavaScript string replacement method and FAQ This article will explore two ways to replace string characters in JavaScript: internal JavaScript code and internal HTML for web pages. Replace string inside JavaScript code The most direct way is to use the replace() method: str = str.replace("find","replace"); This method replaces only the first match. To replace all matches, use a regular expression and add the global flag g: str = str.replace(/fi

Leverage jQuery for Effortless Web Page Layouts: 8 Essential Plugins jQuery simplifies web page layout significantly. This article highlights eight powerful jQuery plugins that streamline the process, particularly useful for manual website creation

So here you are, ready to learn all about this thing called AJAX. But, what exactly is it? The term AJAX refers to a loose grouping of technologies that are used to create dynamic, interactive web content. The term AJAX, originally coined by Jesse J

This post compiles helpful cheat sheets, reference guides, quick recipes, and code snippets for Android, Blackberry, and iPhone app development. No developer should be without them! Touch Gesture Reference Guide (PDF) A valuable resource for desig

jQuery is a great JavaScript framework. However, as with any library, sometimes it’s necessary to get under the hood to discover what’s going on. Perhaps it’s because you’re tracing a bug or are just curious about how jQuery achieves a particular UI

10 fun jQuery game plugins to make your website more attractive and enhance user stickiness! While Flash is still the best software for developing casual web games, jQuery can also create surprising effects, and while not comparable to pure action Flash games, in some cases you can also have unexpected fun in your browser. jQuery tic toe game The "Hello world" of game programming now has a jQuery version. Source code jQuery Crazy Word Composition Game This is a fill-in-the-blank game, and it can produce some weird results due to not knowing the context of the word. Source code jQuery mine sweeping game

Article discusses creating, publishing, and maintaining JavaScript libraries, focusing on planning, development, testing, documentation, and promotion strategies.

This tutorial demonstrates how to create a captivating parallax background effect using jQuery. We'll build a header banner with layered images that create a stunning visual depth. The updated plugin works with jQuery 1.6.4 and later. Download the


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

PhpStorm Mac version
The latest (2018.2.1) professional PHP integrated development tool

MantisBT
Mantis is an easy-to-deploy web-based defect tracking tool designed to aid in product defect tracking. It requires PHP, MySQL and a web server. Check out our demo and hosting services.

SublimeText3 Linux new version
SublimeText3 Linux latest version

SecLists
SecLists is the ultimate security tester's companion. It is a collection of various types of lists that are frequently used during security assessments, all in one place. SecLists helps make security testing more efficient and productive by conveniently providing all the lists a security tester might need. List types include usernames, passwords, URLs, fuzzing payloads, sensitive data patterns, web shells, and more. The tester can simply pull this repository onto a new test machine and he will have access to every type of list he needs.

EditPlus Chinese cracked version
Small size, syntax highlighting, does not support code prompt function
