The line marked below is not complete. Should it be competed with " val2);".

Number.prototype.add=function(val1,val2) { return val1 + val2; };
var num = new Number();
num.prototype.add = function(val1, <<<----
var sum = num.add(8,3); // sum is 11

Note from the Author or Editor:
The following line should be removed (it was left in by accident):

num.prototype.add = function(val1,

The actual example should read:

Number.prototype.add=function(val1,val2) { return val1 + val2; };
var num = new Number();
var sum = num.add(8,3); // sum is 11

The code snippet reads:

if (sValue) // true if a variable is both defined and given a value (including empty string)

This is in error. An empty string evaluates to false, as shown in this code:

var someVar = "";
if (someVar) {
document.writeln("<p>someVar evaluates to TRUE</p>");
}
else {
document.writeln("<p>someVar evaluates to FALSE</p>");
}

Note from the Author or Editor:
The code snippet should read:

if (sValue) // true if a variable is both defined and given a value

The example reads:

var nValue1,nValue2 = 3; // nValue2 is undefined

But it should certainly read:

var nValue1,nValue2 = 3; // nValue1 is undefined

Note from the Author or Editor:
The current 6th example in Section 3.2 and the line of text preceding it currently read:

However, with the following, where variables are lined up with commas between them, the first variable is set and the second ends up undefined:

var nValue1,nValue2 = 3; // nValue2 is undefined

It should read:

However, with the following, where variables are lined up with commas between them, the second variable is set, and the first ends up undefined:

var nValue1,nValue2 = 3; // nValue1 is undefined

The flags value is set to 0101, and the flag 'order' is apparently ABCD (A/C false, B/D true).

[quote]
flag A: false
flag B: true
flag C: false
flag D: true
[/quote]

>> C is false!

But then the flag order is reversed to DCBA:

[quote]
Each bit mask flag is then represented as follows:
var flag_A = 0x1; // 0001
var flag_B = 0x2; // 0010
var flag_C = 0x4; // 0100
var flag_D = 0x8; // 1000
[/quote]

>> C is true (suddenly)!

Note from the Author or Editor:
Page 46 in chapter 3, the code example from Mozilla that reads like:

flag A: false
flag B: true
flag C: false
flag D: true

should read:

flag A: true
flag B: false
flag C: true
flag D: false

The values were transposed

In discussing the parseInt function, the example indicates that parseInt("266",16) results in a value of 550. Although my understanding of converting to hex and octal is rudimentary, my code indicate that the result is 614, not 550. I'm not sure if the difference between my result and that of the author is my mistake or not, but I ran the code verbatim, and my result is different.

Note from the Author or Editor:
The use of parseInt("266","16") shown in page 33, paragraph 5, results in a value of 614, not 550 as shown in the book.