module("About Functions And Closure (topics/about_functions_and_closure.js)");

test("defining functions directly", function() {

var result = "a";

function changeResult() {

// the ability to access a variables defined in the same scope as the function is known as 'closure'

result = "b";

};

changeResult();

equals(result, __, 'what is the value of result?');

});

test("assigning functions to variables", function() {

var triple = function(input) {

return input * 3;

};

equals(triple(4), __, 'what is triple 4?');

});

test("self invoking functions", function() {

var publicValue = "shared";

// self invoking functions are used to provide scoping and to alias variables

(function(pv) {

var secretValue = "password";

equals(pv, __, 'what is the value of pv?');

equals(typeof(secretValue), "__", "is secret value available in this context?");

equals(typeof(pv), "__", "is public value available in this context?");

})(publicValue);

equals(typeof(secretValue), "__", "is secret value available in this context?");

equals(typeof(publicValue), "__", "is public value available in this context?");

});

test("arguments array", function() {

var add = function() {

var total = 0;

for(var i = 0; i < arguments.length; i++) {

// complete the implementation of this method so that it returns the sum of its arguments

}

// __

};

equals(add(1,2,3,4,5), 15, "add 1,2,3,4,5");

equals(add(4,7,-2), 9, "add 1,2,3,4,5");

});

test("using call to invoke function",function(){

var invokee = function( message ){

return this + message;

};

//another way to invoke a function is to use the call function which allows

//you to set the callers "this" context. Call can take any number of arguments:

//the first one is always the context that this should be set to in the called

//function, and the arguments to be sent to the function,multiple arguments are separated by commas.

var result = invokee.call("I am this!", "Where did it come from?");

equals(result,__,"what will the value of invokee's this be?");

});

test("using apply to invoke function",function(){

var invokee = function( message1, message2 ){

return this + message1 + message2;

};

//similar to the call function is the apply function. Apply only has two

//arguments: the first is the context that this should be set to in the called

//function and and array of arguments to be passed into the called function.

var result = invokee.apply("I am this!", ["I am arg1","I am arg2"]);

equals(result,__,"what will the value of invokee's this be?");

});