Browser Questions

Table of Contents

• Origin
• CORS
• HTTP Caching
• HTMLCollection and NodeList

Origin

• Web content’s origin is defined by the scheme (protocol), hostname (domain), and port of the URL used to access it.
• Two objects have the same origin only when the scheme, hostname and port all match.

References

• https://developer.mozilla.org/en-US/docs/Glossary/Origin

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CORS

• Cross-Origin Resource Sharing (CROS) is an HTTP-header based mechanism that allows a server to indicate any origins other than its own from which a browser should permit loading of resources.
• Three scenarios:
  • Simple requests don’t trigger a CORS preflight.
  • Preflighted requests.
  • Requests with credentials.

References

• https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS#what_requests_use_cors

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HTTP Caching

• Different kinds of caches
  • Private browser caches
  • Shared proxy caches
  • Other caches…
• Terminology
  • Stale Content
  • Fresh Content
  • Cache Validation
  • Cache Invalidation
• How does the content get cached?
  • Whenever the server sends the response to the client, it sends the HTTP headers in the response, which are then used by the client or any other intermediate places to cache the content.
  • Caching headers
    • Expires
    • Pragma
    • Cache-Control
• How is the validation of cache checked from the server?
  • ETag (Entity Tags)
  • Last-Modified

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HTMLCollection and NodeList

HTMLCollection

• A generic collection (array-like object similar to arguments) of elements (in document order) and offer methods and properties from selecting from the list.
• An HTMLCollection in the HTML DOM is live; it is automatically updated when the underlying document is changed.

NodeList

• NodeList objects are collections of nodes, not an Array.
• 2 varieties: live and static.

References

• https://developer.mozilla.org/en-US/docs/Web/API/HTMLCollection
• https://developer.mozilla.org/en-US/docs/Web/API/NodeList

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