WebFund 2013F Lecture 4

Audio from the lecture given on September 18, 2013 is available here

Readings

September 18

empty object
- foo={ };
delegation : waiting for another object to do your work
- similar to inheritance in java
delegation of objects happens in the prototype property
every object has a default prototype
everything delegates to object
- similar to inherits but there are no classes and no hierarchy
object reflection
- look inside an object and see what's there
for loops in javascript

	for(p in foo){
	
	}

- similar to a for each loop in java
- will iterate through all the properties in foo, no fixed order
- DO NOT DO THIS
- follows prototype and looks at the properties in the entire prototype chain
typeof(foo.x) can tell you if x is
- number
- string
- object
foo.hasOwnProperty('x') returns true or false
for loops that don't care about the prototype chain
- create an array that has the properties you want and iterate through them
vector array uses [] instead of {}
- ie. [5, hello, etc];
- use an array because they're ordered!
foo.x is equivalent to foo["x"]
- objects are like associative arrays where you index by letters/strings

dynamic
- symbols you can access and the meaning of them depends on what code has been run before hand
- x=7;
- x=3;
- x is what part came first
- global variables are inheritently global scoped
lexical/textual
- - variables it can see depends on what is around it
  - idea of local variables
javascript has a very important global score
create a namespace to keep global script from getting too big
- but doesn't exist in a standardized form
global abatement - minimize what you write in the global scope
local variable, say var in front of it
no block scope in javascript, function scope is not block scope

f = function(a){
	return function(b)[
		return a+b;
	}
}; // data encapsulation 
g = t(5); g(7); returns 12