Chapter 2.txt

Listing 2-1. Declaring a Variable
var num0;
var num1;
var sum; 


Listing 2-2. Assigning Values to Variables
num0 = 100;
num1 = 200;


Listing 2-3. Adding Variables
sum = num0 + num1; 


Listing 2-4. Changing the Order of Operations with Parentheses
var result0 = 1 + 2 * 3;	//result0 will be 7
var result1 = (1 + 2) * 3;	//result1 will be 9


Listing 2-5. Displaying the Value of Sum on the Screen
document.write(“Total amount = “ + sum);


Listing 2-6. Manipulating a Variable by Referencing Itself
var score = 10;
score = score + 20;
document.write(score);


Listing 2-7. Declaring and Incrementing a Variable
var num = 1;
num++;
document.write(num);


Listing 2-8. Incrementing a Variable within a Statement
var num = 1;
document.write(num++);
num = 1;
document.write(++num);


Listing 2-9. Comparing Values
var num0 = 4;
var num1 = 7;
document.write(num0 >= num1);
document.write(num0 < num1);
document.write(num0 === num1);


Listing 2-10. Differing Equivalent Operators
var num0 = 4;
var num1 = “4”;
document.write(num0 == num1);
document.write(num0 === num1);


Listing 2-11. Manipulating Comparisons
document.write(!(4 > 3));
document.write((4 < 7) && (5 < 13));
document.write((4 > 5) || (4 < 5));


Listing 2-12. Implementing Logic with the If Statement
var num0 = 4;
var num1 = 8;
if (num0 >= num1) {
    document.write(num0 + “ is greater than or equal to ” + num1 + “.”);
}
else if (num0 < num1) {
    document.write(num0 + “ is less than ” + num1 + “.”); 
}


Listing 2-13. Creating the Date Object
var date = new Date();


Listing 2-14. Assigning Date Information to Variables
var y = date.getFullYear();
var m = date.getMonth() + 1;
var d = date.getDate();


Listing 2-15. Creating a String and Displaying It
var text = "The date is " + m + "/" + d + "/" + y;
document.write(text);


Listing 2-16. An Impractical Way to Add Sequential Numbers
int num = 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 + 11 + 12 + 13 + 14 + 15 + 16 + 17 + 18 + 19 + 20 + 21 + 22 + 23 + 24 + 25 + 26 + 27 + 28 + 29 + 30 + 31 + 32 + 33 + 34 + 35 + 36 + 37 + 38 + 39 + 40 + 41 + 42 + 43 + 44 + 45 + 46 + 47 + 48 + 49 + 50 + 51 + 52 + 53 + 54 + 55 + 56 + 57 + 58 + 59 + 60 + 61 + 62 + 63 + 64 + 65 + 66 + 67 + 68 + 69 + 70 + 71 + 72 + 73 + 74 + 75 + 76 + 77 + 78 + 79 + 80 + 81 + 82 + 83 + 84 + 85 + 86 + 87 + 88 + 89 + 90 + 91 + 92 + 93 + 94 + 95 + 96 + 97 + 98 + 99 + 100;


Listing 2-17. Creating Variables
var i;
var sumFor;
var sumWhile;


Listing 2-18. The While Loop
sumWhile = 0;
i = 1;
while (i <= 100) {
	sumWhile += i;
	i++;
}
document.write(“The result using a while loop: ” + sumWhile + “<BR />”);


Listing 2-19. The For Loop
sumFor = 0;
for (i = 1; i <= 100; i++) {
sumFor += i;
}
document.write("The result using a for loop: " + sumFor + “<BR />”);


Listing 2-20. Breaking Out of A Loop
var sumWhile = 0; 
var i = 1; 
while (true) { 
    sumWhile += i; 
    i++; 
    if (i > 100) break; 
} 
document.write(sumWhile);


Listing 2-21. Using Continue to Skip Odd Numbers
var sumFor = 0; 
for (i = 1; i <= 100; i++) { 
    if (i % 2 != 0) continue; 
    sumFor = sumFor + i;
} 
document.write(“The sum of all even numbers up to 100 is ” + sumFor);


Listing 2-22. Creating Variables for the Fortune-Telling Game
var num;
var text = "";
num = Math.floor(Math.random() * 4);


Listing 2-23. Fortune Telling with the If Statement
if (num===0) {
    text = "Super Lucky";
} else if (num===1) {
    text = "So-so Luck";
} else if (num===2) {
    text = "Minor Luck";
} else {
    text = "Bad Luck";
}
document.write("Your fortune: " + text);


Listing 2-24. Setting Up for the Switch Example
var num;
var text = "";
num = Math.floor(Math.random() * 4);


Listing 2-25. The Fortune-Telling Switch Statement
switch (num) {
case 0:
textSwitch = "Excellent Luck";
break;
case 1:    
textSwitch = "Moderate Luck";
break;
case 2:    
textSwitch = "Small Luck";
break;
default:    
textSwitch = "Bad Luck";
break;
}


Listing 2-26. Creating an Array of Devices
var array = new Array(3);
array[0] = "iPhone";
array[1] = "Android";
array[2] = "Computer";


Listing 2-27. Iterating Through an Array
var text = "";
for (var i = 0; i < array.length; i++) {
    text += array[i] + "<BR />";
}
document.write(text);


Listing 2-28. Creating an Associative Array
var obj = new Object();
obj["iPhone"]     = "White";
obj["Android"]    = "Black";
obj["Computer"]   = "Silver";


Listing 2-29. Manually Iterating Through the Associative Array
var textObj = "";
textObj += “The iPhone is ” + obj["iPhone"] + ".<BR />";
textObj += “The Android is ” + obj["Android"] + ".<BR />";
textObj += “The Computer is ” + obj["Computer"] + ".<BR />";
document.write(textObj);


Listing 2-30. Defining the buy() Function
function buy(device) {
    document.write("I will buy the " + device + ".<BR />");
}


Listing 2-31. Calling the Function
buy(“iPhone”);
buy(“Android”);


Listing 2-32. Making King Bob
var bob = 39;


Listing 2-33. Creating a Function to Create a Random Bob
function villager() {
	var bob = Math.floor(Math.random() * 50 + 10);
	this.bob += 1;
	document.write(“King Bob’s age is ” + bob + “.<BR />”);
	document.write(“Villager Bob, this Bob, is ” + this.bob + “.”);
}


Listing 2-34. Calling the Villager Function
Villager();


Listing 2-35. Creating the Prototype and Properties
function Software() {
}


Listing 2-36. Creating The Prototype Function
Software.prototype.output = function() {
    document.write(this.name + " is written in " + this.language + "<BR />");
};


Listing 2-37. Creating the Accounting Object
var accounting = new Software();

accounting.name     = "Spreadsheet Master";
accounting.language = "Java";

accounting.output();