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Using CORS

Using CORS
Introduction APIs are the threads that let you stitch together a rich web experience. But this experience has a hard time translating to the browser, where the options for cross-domain requests are limited to techniques like JSON-P (which has limited use due to security concerns) or setting up a custom proxy (which can be a pain to set up and maintain). Cross-Origin Resource Sharing (CORS) is a W3C spec that allows cross-domain communication from the browser. By building on top of the XMLHttpRequest object, CORS allows developers to work with the same idioms as same-domain requests. The use-case for CORS is simple. As you can see from this example, CORS support requires coordination between both the server and client. Making a CORS Request This section shows how to make a cross-domain request in JavaScript. Creating the XMLHttpRequest object CORS is supported in the following browsers: Chrome, Firefox, Opera and Safari all use the XMLHttpRequest2 object. Event handlers withCredentials Resources

Moment.js | Home HTTP access control (CORS) - HTTP A resource makes a cross-origin HTTP request when it requests a resource from a different domain than the one which the first resource itself serves. For example, an HTML page served from makes an <img> src request for Many pages on the web today load resources like CSS stylesheets, images and scripts from separate domains. For security reasons, browsers restrict cross-origin HTTP requests initiated from within scripts. For example, XMLHttpRequest and Fetch follow the same-origin policy. So, a web application using XMLHttpRequest or Fetch could only make HTTP requests to its own domain. The Cross-Origin Resource Sharing (CORS) mechanism gives web servers cross-domain access controls, which enable secure cross-domain data transfers. This article is for web administrators, server developers, and front-end developers. This cross-origin sharing standard is used to enable cross-site HTTP requests for: Overview Simple requests Origin See also

Underscore.js Cross-Origin Resource Sharing Abstract This document defines a mechanism to enable client-side cross-origin requests. Specifications that enable an API to make cross-origin requests to resources can use the algorithms defined by this specification. If such an API is used on resources, a resource on can opt in using the mechanism described by this specification (e.g., specifying Access-Control-Allow-Origin: as response header), which would allow that resource to be fetched cross-origin from Status of this Document This section describes the status of this document at the time of its publication. This document has been reviewed by W3C Members, by software developers, and by other W3C groups and interested parties, and is endorsed by the Director as a W3C Recommendation. If you wish to make comments regarding this document, please send them to (subscribe, archives). Table of Contents 1 Introduction 2 Conformance The .

How to return the response from an Ajax call? Cross-Domain Requests with CORS Cross-Origin Resource Sharing (CORS) is a powerful technology for static web apps. To understand what it is and why it's important, you first need to understand a bit about how browsers work. The Same-Origin Policy The Same-Origin Policy restricts the browser from performing certain actions by scripts or documents based on the origin. A parent document can't access the contents of an <iframe> that comes from a different origin. The Same-Origin Policy is a vital piece of web security architecture, but it also poses a problem. Enter Cross-Origin Resource Sharing CORS allows you to more cleanly separate your front-end from your back-end. If you are building an application using a third-party data provider or an API that already supports CORS, there isn't much else you need to know! Implementing CORS CORS is a group of special response headers sent from the server that tell a browser whether or not to allow the request to go through. Access-Control-Allow-Origin:

Essential jQuery Plugin Patterns Advertisement I occasionally write about implementing design patterns1 in JavaScript. They’re an excellent way of building upon proven approaches to solving common development problems, and I think there’s a lot of benefit to using them. But while well-known JavaScript patterns are useful, another side of development could benefit from its own set of design patterns: jQuery plugins. The official jQuery plugin authoring guide2 offers a great starting point for getting into writing plugins and widgets, but let’s take it further. Plugin development has evolved over the past few years. Some developers may wish to use the jQuery UI widget factory3; it’s great for complex, flexible UI components. I began to think about plugin patterns after noticing a number of efforts to create a one-size-fits-all jQuery plugin boilerplate. Let’s assume that you’ve tried your hand at writing your own jQuery plugins at some point and you’re comfortable putting together something that works. Patterns And so on.

CORS Enabled - W3C Wiki What is CORS about? CORS is a specification that enables truly open access across domain boundaries. Why is CORS important? Currently, client-side scripts (e.g., JavaScript) are prevented from accessing much of the Web of Linked Data due to "same origin" restrictions implemented in all major Web browsers. While enabling such access is important for all data, it is especially important for Linked Open Data and related services; without this, our data simply is not open to all clients. If you have public data which doesn't use require cookie or session based authentication to see, then please consider opening it up for universal JavaScript/browser access. For CORS access to anything other than simple, non auth protected resources please see this full write up on Cross Origin Request Security. How can I participate? Granting JavaScript clients basic access to your resources simply requires adding one HTTP Response Header, namely: At the HTTP Server level... For Apache a2enmod headers For nginx In PHP

.append Description: Insert content, specified by the parameter, to the end of each element in the set of matched elements. The .append() method inserts the specified content as the last child of each element in the jQuery collection (To insert it as the first child, use .prepend()). The .append() and .appendTo() methods perform the same task. The major difference is in the syntax-specifically, in the placement of the content and target. With .append(), the selector expression preceding the method is the container into which the content is inserted. Consider the following HTML: You can create content and insert it into several elements at once: Each inner <div> element gets this new content: You can also select an element on the page and insert it into another: If an element selected this way is inserted into a single location elsewhere in the DOM, it will be moved into the target (not cloned): Additional Arguments

Making Cross-Domain Requests with CORS One thing I ask interview candidates is how to make cross-domain requests with Javascript. All too often, interviewees only come up with JSON-P and proxying as a solution. This is insufficient for JS devs in 2012. Johnny Wey has a great write up on JSON-P and why you might not want to use it. Libraries like jQuery will handle all of the complexities of this and gracefully degrade to other technologies as much as possible, but it is important for JSers to know what is going on under the covers. That’s where this post comes in. Background HTTP requests from Javascript are traditionally bound by the Same Origin Policy, which means that your ajax requests must have the same domain and port. CORS stands for Cross-Origin Resource Sharing. Why you should use CORS Compared to proxying, the significant advantage of CORS is not having another system component, possibly complicating the app. It has a few big advantages over JSON-P as well: How CORS works GET Simple vs.

Understanding Cross-Origin Resource Sharing (CORS) Note: This is a pretty trivial example I created for the purposes of illustration. I intentionally did not use of any frameworks. The onLoadHandler() function creates an XMLHttpRequest and opens it for a GET request to the GitHub API URL. The third parameter for the open method, is set to true, and specifies that this request is asynchronous. Next, the code snippets create the event handlers for the request. We are only handling the onload and onerror events but there are a number of other events available using CORS including onloadstart, onprogress, onabort, ontimeout, and onloadend events. Chrome, FireFox, Opera, Safari browsers Chrome supported CORS through the XMLHttpRequest level 2 as of version 3 (which seems like ages ago). Internet Explorer Sadly, Internet Explorer is the only browser that merits its own section here.

ajax - CORS - What is the motivation behind introducing preflight requests?