#web concepts
Origin
Web content's origin is defined by the scheme (protocol), host (domain), and port of the URL used to access it. Two objects have the same origin only when the scheme, host, and port all match.
Some operations are restricted to same-origin content, and this restriction can be lifted using CORS.
Origin
Web content's origin is defined by the scheme (protocol), host (domain), and port of the URL used to access it. Two objects have the same origin only when the scheme, host, and port all match.
Some operations are restricted to same-origin content, and this restriction can be lifted using CORS.
#web concepts
Asynchronous
The term asynchronous refers to two or more objects or events not existing or happening at the same time (or multiple related things happening without waiting for the previous one to complete). In computing, the word "asynchronous" is used in two major contexts.
Networking and communications
Asynchronous communication is a method of exchanging messages between two or more parties in which each party receives and processes messages whenever it's convenient or possible to do so, rather than doing so immediately upon receipt. Additionally, messages may be sent without waiting for acknowledgement, with the understanding that if a problem occurs, the recipient will request corrections or otherwise handle the situation.
For humans, e-mail is an asynchronous communication method; the sender sends an email and the recipient will read and reply to the message when it's convenient to do so, rather than doing so at once. And both sides can continue to send and receive messages whenever they wish, instead of having to schedule them around each other.
When software communicates asynchronously, a program may make a request for information from another piece of software (such as a server), and continue to do other things while waiting for a reply. For example, the AJAX (Asynchronous JavaScript and XML) programming technique—now usually simply "Ajax", even though JSON is usually used rather than XML in modern applications—is a mechanism that requests relatively small amounts of data from the server using HTTP, with the result being returned when available rather than immediately.
Software design
Asynchronous software design expands upon the concept by building code that allows a program to ask that a task be performed alongside the original task (or tasks), without stopping to wait for the task to complete. When the secondary task is completed, the original task is notified using an agreed-upon mechanism so that it knows the work is done, and that the result, if any, is available.
Asynchronous
The term asynchronous refers to two or more objects or events not existing or happening at the same time (or multiple related things happening without waiting for the previous one to complete). In computing, the word "asynchronous" is used in two major contexts.
Networking and communications
Asynchronous communication is a method of exchanging messages between two or more parties in which each party receives and processes messages whenever it's convenient or possible to do so, rather than doing so immediately upon receipt. Additionally, messages may be sent without waiting for acknowledgement, with the understanding that if a problem occurs, the recipient will request corrections or otherwise handle the situation.
For humans, e-mail is an asynchronous communication method; the sender sends an email and the recipient will read and reply to the message when it's convenient to do so, rather than doing so at once. And both sides can continue to send and receive messages whenever they wish, instead of having to schedule them around each other.
When software communicates asynchronously, a program may make a request for information from another piece of software (such as a server), and continue to do other things while waiting for a reply. For example, the AJAX (Asynchronous JavaScript and XML) programming technique—now usually simply "Ajax", even though JSON is usually used rather than XML in modern applications—is a mechanism that requests relatively small amounts of data from the server using HTTP, with the result being returned when available rather than immediately.
Software design
Asynchronous software design expands upon the concept by building code that allows a program to ask that a task be performed alongside the original task (or tasks), without stopping to wait for the task to complete. When the secondary task is completed, the original task is notified using an agreed-upon mechanism so that it knows the work is done, and that the result, if any, is available.
#web concepts
CDN
A CDN (Content Delivery Network) is a group of servers spread out over many locations. These servers store duplicate copies of data so that servers can fulfill data requests based on which servers are closest to the respective end-users. CDNs make for fast service less affected by high traffic.
CDNs are used widely for delivering stylesheets and Javascript files (static assets) of libraries like Bootstrap, jQuery etc. Using CDN for those library files is preferable for a number of reasons:
Serving libraries' static assets over CDN lowers the request burden on our own servers.
Most CDNs have servers all over the globe so CDN's servers may be geographically nearer to your users than your own servers. Geographical distance affects latency proportionally.
CDNs are already configured with proper cache settings. Using a CDN saves further configuration for static assets on your own servers.
CDN
A CDN (Content Delivery Network) is a group of servers spread out over many locations. These servers store duplicate copies of data so that servers can fulfill data requests based on which servers are closest to the respective end-users. CDNs make for fast service less affected by high traffic.
CDNs are used widely for delivering stylesheets and Javascript files (static assets) of libraries like Bootstrap, jQuery etc. Using CDN for those library files is preferable for a number of reasons:
Serving libraries' static assets over CDN lowers the request burden on our own servers.
Most CDNs have servers all over the globe so CDN's servers may be geographically nearer to your users than your own servers. Geographical distance affects latency proportionally.
CDNs are already configured with proper cache settings. Using a CDN saves further configuration for static assets on your own servers.
#web concept
CORS
CORS (Cross-Origin Resource Sharing) is a system, consisting of transmitting HTTP headers, that determines whether browsers block frontend JavaScript code from accessing responses for cross-origin requests.
The same-origin security policy forbids cross-origin access to resources. But CORS gives web servers the ability to say they want to opt into allowing cross-origin access to their resources.
CORS
CORS (Cross-Origin Resource Sharing) is a system, consisting of transmitting HTTP headers, that determines whether browsers block frontend JavaScript code from accessing responses for cross-origin requests.
The same-origin security policy forbids cross-origin access to resources. But CORS gives web servers the ability to say they want to opt into allowing cross-origin access to their resources.
rh_yum_cheatsheet_1214_jcs_print-1.pdf
102 KB
Emailing rh_yum_cheatsheet_1214_jcs_print-1.pdf
Forwarded from Hadi
آمریکا ۸۰ تا کانال تلویزیونی خودش رو به صورت لایو و مجانی در اینترنت ارائه کرده روی لینک بزنید تا لیست کانال ها را ببینید و از هر کدوم که خواستید در موبایل استفاده کنید
https://ustvgo.tv/
https://ustvgo.tv/
rfc6455.pdf
235.2 KB
rfc6455.pdf
WebSocket protocol
WebSocket protocol
#web concepts
Short polling vs. Long polling
With the traditional or "short polling" technique, a client sends regular requests to the server and each request attempts to "pull" any available events or data. If there are no events or data available, the server returns an empty response and the client waits for some time before sending another poll request. The polling frequency depends on the latency that the client can tolerate in retrieving updated information from the server. This mechanism has the drawback that the consumed resources (server processing and network) strongly depend on the acceptable latency in the delivery of updates from server to client. If the acceptable latency is low (e.g., on the order of seconds), then the polling frequency can cause an unacceptable burden on the server, the network, or both.
In contrast with such "short polling", "long polling" attempts to minimize both the latency in server-client message delivery and the use of processing/network resources. The server achieves these efficiencies by responding to a request only when a particular event, status, or timeout has occurred. Once the server sends a long poll response, typically the client immediately sends a new long poll request. Effectively, this means that at any given time the server will be holding open a long poll request, to which it replies when new information is available for the client. As a result, the server is able to asynchronously "initiate" communication.
Short polling vs. Long polling
With the traditional or "short polling" technique, a client sends regular requests to the server and each request attempts to "pull" any available events or data. If there are no events or data available, the server returns an empty response and the client waits for some time before sending another poll request. The polling frequency depends on the latency that the client can tolerate in retrieving updated information from the server. This mechanism has the drawback that the consumed resources (server processing and network) strongly depend on the acceptable latency in the delivery of updates from server to client. If the acceptable latency is low (e.g., on the order of seconds), then the polling frequency can cause an unacceptable burden on the server, the network, or both.
In contrast with such "short polling", "long polling" attempts to minimize both the latency in server-client message delivery and the use of processing/network resources. The server achieves these efficiencies by responding to a request only when a particular event, status, or timeout has occurred. Once the server sends a long poll response, typically the client immediately sends a new long poll request. Effectively, this means that at any given time the server will be holding open a long poll request, to which it replies when new information is available for the client. As a result, the server is able to asynchronously "initiate" communication.
rfc2616.pdf
537.7 KB
rfc2616.pdf
HTTP Protocol
HTTP Protocol
HTML 5.1 2nd Edition
https://www.w3.org/TR/html51/
https://www.w3.org/TR/html51/