IML400-Magic Card Trick Getting Started

magicCardTrick.js

//the number between 1-27
var favoriteNumber = 10;
// a list of 27 cards; here I am using 
// S = spades, C = clubs, D = diamonds, H = hearts
var cards = ["2C","3C","4C",
			 "5C","6C","7C",
			 "8C","9C","10C",
			 "2S","3S","4S",
			 "5S","6S","7S",
			 "8S","9S","10S",
			 "2H","3H","4H",
			 "5H","6H","7H",
			 "8H","9H","10H"]

// convert a decimal number (base 10) to a 
// base 3 number
function convertToBase3(aNumber) {
	if( aNumber > 26) {
		console.log('this function only works for numbers between 1 and 27')
		return "000"
	}
	if( aNumber < 1) {
		console.log('this function only works for numbers between 1 and 27')
		return "000"
	}
		
	//how many times does 9 go into our number. Stated another way
	// how many times can we take 9 away from our number?	
	var nines = Math.floor(aNumber / 9)

	// Ok, now take that many number of nines away and see how much we have left over
	var ninesRemainder = aNumber - (nines * 9)

	//Now how many times can we take 3 away from the remainder?
	var threes = Math.floor( ninesRemainder / 3)

	// Take that number of 3's away from the remainder
	var threesRemainder = ninesRemainder - (threes * 3)

	//Finally what is remaining is the number that will go in the 1's column
	//This is the remainder after we have taken away all the 9's and the 3's
	// To be explicit this is what we are doing 

	var ones = Math.floor(threesRemainder / 1)

	//Now we smash together the nines, threes and ones to make our base 3 Number
	//We are going to store it as a string NOT a number. This is just like we store
	// Hexadecimal numbers for colors: "#AB108C" for instance
	var baseThreeNumber = "" + nines + threes + ones

	return baseThreeNumber

}


// given a base 3 number get the number that appears in the 9's column.
// For example given the base 3 number 021 or 21, this function would return 0
function getThe9Column(aBase3Number) {
	if(aBase3Number.length > 3) {
		console.log('this function only works for base3 numbers that are 3 digits long or less')
		return 0;
	}

	if(aBase3Number.length < 3) {
		return 0	
	} else {
		return aBase3Number.substr(0,1);
	}
}

// given a base 3 number get the number that appears in the 3's column.
// For example given the base 3 number 021 or 21, this function would return 2
function getThe3Column(aBase3Number) {
	if(aBase3Number.length > 3) {
		console.log('this function only works for base3 numbers that are 3 digits long or less')
		return 0;
	}	
	if(aBase3Number.length < 2) {
		return 0	
	} else {
		return aBase3Number.substr(1,1);
	}	
}

// given a base 3 number get the number that appears in the 1's column.
// For example given the base 3 number 021 or 21, this function would return 1
function getThe1Column(aBase3Number) {
	if(aBase3Number.length > 3) {
		console.log('this function only works for base3 numbers that are 3 digits long or less')
		return 0;
	}
	if(aBase3Number.length < 1) {
		return 0	
	} else {
		return aBase3Number.substr(2,1);
	}		
}


/* to test it out:
 Open Chrome Developer Tools:
 View >> Developer >> Javascript Console

 and paste this file into the console.

 To test the function just enter the following into the console
*/
 console.log("Converting the number " + favoriteNumber + " to base 3 = ")
 var result = convertToBase3(favoriteNumber)
 console.log( result )

//if you want to test different numbers just enter the following into the console

console.log( convertToBase3(27) )

console.log( getThe9Column("210") )
console.log( getThe3Column("210") )
console.log( getThe1Column("210") )