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A web app is broken to frontend (obvious) and backend (at the least because there's always code you don't want to be seen by browsers). The two communicate via http protocol (whether encrypted or not).

http/https misc

  • raw protocol methods are plain-text with lines ending with \r\n, where:
    1. 1-st line: space-separated method name, URL, protocol version. Example: GET /image/logo.png HTTP/1.1
    2. one or more header lines (Host is mandatory, the rest are not), e.g.: 
      Host: www.example.com
Accept-Language: en
    3. empty line
    4. optionally: message body.
  • protocol is stateless, so a user session is managed with cookies.
  • methods used most frequently:
    • GET: should only retrieve data and have no other effect.
    • HEAD: like GET but for metadata. E.g. retrieving data length.
    • POST: asking server to process some data and mutate some state.
    • PUT: like POST but allows specifying target location and is uncacheable.
  • methods result in reply from the server containing a code, and optionally some other fields and HTML or other data depending on the circumstances.

REST

Basically an API built upon HTTP requests. You have a URL (which includes path and optionally a query) and HTTP headers. And then you call POST/GET/etc with all this stuff.

When building REST yourself, it's interesting that data may be transferred via URL path, a URL query or headers. The general opinion is: prefer URL path&query unless it becomes inconvenient or dealing with security-related stuff. Someone also notes that proxies may strip headers. Also, path&query works without js.

A minimal example of making a POST request: curl --request POST http://example.com/bar/buzz. Note that we don't pass any data as it's not required; for example when everything is passed inside the URL.

javascript misc

JS has no static typing, so you don't want to develop in it directly. Instead it is like assembly of the web (not to be confused with WebAssembly), and you'd code in another language that will get translated to JS. Of others: there's TypeScript, but its typing system is just terrible (broken immutability, equality tests not failing for distinct types…). Next one is PureScript. It has excellent type system but might be complicated for newbies. So basically, web-devel here is like the tale of two stools.

PureScript has a separate file.

HTML

  • sidebar: nav with ul and li.
  • title-bar: header (not to be confused with h1, etc).
  • grouping HTML elements for styling or other purposes: div tag.
  • form causes page reload upon sending GET or POST: there's a hack with creating somewhere a tag <iframe name="/dev/null" style="display:none;"></iframe> and then using a target="/dev/null" as a form property.