js401-reading

Readings: Classes, Inheritance, Functional Programming

Functional Programming

• Functional programming is the distinction between pure code (no side effects) and impure code
  • procedural is a sequence of steps
  • object oriented is solution as communicating objects
  • functional is modeling as pure functions
• Pure Functions give a value based on ONLY what it was passed
  • outside variables are an example of impure functions
• high order functions are passed other functions or return a function
  • higher order functions are things like map, filter, reduce

Objects and Inheritance

• JS has prototype-based inheritance rather than Class Based inheritance
• for classes… function() becomes class{} call() becomes extends

Errors

• good error messages make debugging much easier
  1. timestamp
  2. message about the problem
  3. cause of problem
  4. consistent format
  5. severity level (low-high, 0-10)
• JS can throw an error on command which lets them be caught rather than breaking the whole app
• extensive lists of System Errors can help debug
  • EACCESS - an attempt to access a file without the right permissions
  • EADDRINUSE - an attempt to start a server on a PORT that is already in use
  • ECONNREFUSED - a connection was deliberately refused by the target machine
  • ECONNRESET - a connection was forcibly closed by a peer
  • EEXIST - a file exists and the attempted action required that it didn’t
  • EISDIR - an action expected to act on a file but found a directory
  • EMFILE - too many files were open for your operating system to handle
  • ENOENT - an action expected a file, but did not find one
  • ENOTDIR - an action expected a directory, but found something else
  • ENOTEMPTY - an action expected an empty directory, but found one with data in it
  • EPERM - an attempt to do something that you currently don’t have permissions to do
  • EPIPE - an attempt to write data to a connection that had been closed

Addtional Materials context

• what this is at a given time
• default is the window object
  • inside of an object this is the object itslef (such as in a function)
• ways to set context call, apply, bind
  • can change the context of a specific function on the go
  • call takes the args (context, n,n+1)
  • apply takes the args (context, [])
  • bind forces a context if you save a variant function with the bind
• using this you can save the current this to a variable and then pass that later on

Inheritance and the prototype chain

this

classes

node error docs

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