## Function Parameters 

There are two schools of thought on passing function parameters.

The first you are probably more familiar with, where parameters must all be included in order. This is the standard approach in Javascript. The second is passing parameters by name. This is less familiar.

There are advantages to both methods, and disadvantages. You may choose to create functions that operate either way, but you must always call them consistently -- a function with named parameters can't be called without naming the parameters.

#### Parameters by Order

    // define a function
    
    set ByOrder task given first, second, third
      debug first + second + third
      
    // call it
    
    ByOrder "a", "b", "c"
    
    // results
    > abc

In Javascript, this looks like the following:

    var ByOrder = function(first, second, third) {
      console.log(first+second+third);
    }

    ByOrder("a","b","c");
    
    > abc
    
#### Parameters by Name

    // define a function
    
    set ByName task 
      debug $first + $second + $third
    
    // call it
    // note the colon after the verb
    
    ByName: first 'a', second 'b', third 'c'
    
    > abc
    
In Javascript:

    var ByName = function(p) {
      console.log(p.first+p.second+p.third);
    }

    ByName({first:'a', second:'b', third:'c'});
    
    > abc
    
### What's happening?

When you call a function passing parameters by name, you're passing in an object with those parameters as attributes.  Looking closely at the parameter-by-name invocation, the colon signals the beginning of a structure definition. 

On the other side, in a function called with named parameters, the __$__ scoping prefix means look up the named attribute in the first parameter passed in on the function call.  

### What's the point?

Passing a single object, with named attributes, instead of a sequence of values, gives you different ways of approaching code design.

In particular, because named parameters are passed as an object, that object can be re-used from call to call. As well, attributes in that object can be changed, or return values set givenparameters within the object.

#### Parameter/Object re-use

    set parameters: first 'a', second 'b', third 'c'
    ByName parameters

    > abc
    
    set parameters.third d
    ByName parameters

    > abd