/**

    Improve you loop code

*/

var treasureChest = {

    goldCoins: 10000,

    magicalItem : "Crown of Speed",

    necklaces: ["ruby", "pearl", "sapphire", "diamond"],

    openLid: function(){

        alert("openLid");

    }

};

console.log("You found the following necklaces: ");

//

//**BAD**

//

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

    console.log(treasureChest.necklaces[i]);

}

//The code need to do many things:

//1. the value of i

//2. the treasureChest object

//3. necklaces property

//4. the array pointed to by the property

//5. the length property of the array

//Count steps:

//5 steps * (4 loops + 1 check to stop) = 25 steps

/*

    What step we can eliminate?

    Use "cached values" to curtail lengthy, repetitive to the same data

*/

var x = treasureChest.necklaces.length;

for(var i = 0; i < x; i++){

    console.log(treasureChest.necklaces[i]);

}

//Memory access during loop control now only needs to:

//1. retrieve the value of i

//2. retrieve the value of x

//----------- for creating x--------------

//1. ONE TIME COST, creating the variable x in memory

//2-5: the 4 steps finding the value of length

//Count steps:

//2 steps * (4 loops + 1 check to stop) + 5 create extra variable = 15 steps

//So we got 25 - 15 = 10 steps less, imaging we have 10000 datas!

//The difference would be:

//5 steps * (10000 loops + 1 check to stop) = 50005 steps

//2 steps * (10000 loops + 1 check to stop) + 5 extra steps for x = 20007 steps

//The difference would be:

//50005 - 20007 = ~30000 !!!!

/**

    Place your extra control variables inside the loop

*/

for(var i = 0, x = treasureChest.necklaces.length; i < x; i++){

    console.log(treasureChest.necklaces[i]);

}

/**

    Avoid repetitive access at depth

*/

var list = treasureChest.necklaces;

for(var i = 0, x = treasureChest.necklaces.length; i < x; i++){

    console.log(list[i]);

}

/**

    Choose the best loop for arrays,

    for-loop usually better than for-in loop

*/

Array.prototype.countType = function(type){

    ...

}

Array.prototype.removeAll = function(item){

    ...

}

var list = treasureChest.necklaces;

for(p in list){

    console.log(list[i]);

}

//will console out:

//"ruby", "pearl", "sapphire", "diamond", "countType", "removeAll"

//"countType", "removeAll", those are not we want!

//The reason for this is because for-in loop is a property approach to access

//indices will also add in all methods that have been added to the Array prototype.

//prototype makes methods we add becomes Enumerable just like indices.