JavaScript The Definitive Guide Note Part 1

Part 1 Core JavaScript 

Chapter 2. Lexical Structure

2.1 Character Set 

JavaScript programs are written using the Unicode character set.

2.2 Case Sensitivity

2.3. Whitespace and Line Breaks

     JavaScript ignores spaces, tabs, and newlines that appear between tokens in programs

2.4. Optional Semicolons

2.5. Comments

//comments  and /*comments*/

2.6. Literals

2.7. Identifiers

The first character must be a letter, an underscore (_), or a dollar sign ($).

2.8  Reserved Words

Table 2-1. Reserved JavaScript keywords

break	do	if	switch	typeof
case	else	in	this	var
catch	false	instanceof	tHRow	void
continue	finally	new	true	while
default	for	null	try	with
delete	function	return

Table 2-2. Words reserved for ECMA extensions

 

abstract	double	goto	native	static
boolean	enum	implements	package	super
byte	export	import	private	synchronized
char	extends	int	protected	throws
class	final	interface	public	TRansient
const	float	long	short	volatile
debugger

as, is, namespace, and use

Chapter 3. Datatypes and Values

 3.1. Numbers

3.1.1. Integer Literals

represent all integers between -9007199254740992 (-2⁵³) and 9007199254740992 (2⁵³)

3.1.2. Hexadecimal and Octal Literals

0x 0X 0

3.1.3. Floating-Point Literals

[digits][.digits][(E|e)[(+|-)]digits]

Special numeric constants

Constant

Meaning

Infinity	Special value to represent infinity
NaN	Special not-a-number value
Number.MAX_VALUE	Largest representable number
Number.MIN_VALUE	Smallest (closest to zero) representable number
Number.NaN	Special not-a-number value
Number.POSITIVE_INFINITY	Special value to represent infinity
Number.NEGATIVE_INFINITY	Special value to represent negative infinity

3.2. Strings

3.2.2. Escape Sequences in String Literals

Table 3-2. JavaScript escape sequences

Sequence

Character represented

\0	The NUL character (\u0000).
\b	Backspace (\u0008).
\t	Horizontal tab (\u0009).
\n	Newline (\u000A).
\v	Vertical tab (\u000B).
\f	Form feed (\u000C).
\r	Carriage return (\u000D).
\"	Double quote (\u0022).
\'	Apostrophe or single quote (\u0027).
\\	Backslash (\u005C).
\xXX	The Latin-1 character specified by the two hexadecimal digits XX.
\uXXXX	The Unicode character specified by the four hexadecimal digits XXXX.
\XXX	The Latin-1 character specified by the octal digits XXX, between 1 and 377. Not supported by ECMAScript v3; do not use this escape sequence.

3.2.4. Converting Numbers to Strings

String(number) 

Number.toString(number)

toFixed

toExponential

toPrecision

var n = 123456.789;
n.toFixed(0);         // "123457"
n.toFixed(2);         // "123456.79"
n.toExponential(1);   // "1.2e+5"
n.toExponential(3);   // "1.235e+5"
n.toPrecision(4);     // "1.235e+5"
n.toPrecision(7);     // "123456.8"

3.2.5. Converting Strings to Numbers

When a string is used in a numeric context, it is automatically converted to a number.

by simply subtracting zero from it

Number(string_value);
parseInt("ff", 16); //255

parseFloat('string')

3.3. Boolean Values

true  --> 1

false --> 0

true --> 'true'

false --> 'false'

number --> true

0,NaN --> false

'' --> false

'string' --> true

null, undefined --> false

Boolean(arg);

3.4. Functions

function square(x) { return x*x; }

var square = function(x) { return x*x; }

var square = new Function("x", "return x*x;");

3.5. Objects

3.5.1. Creating Objects

var o = new Object( );
var now = new Date( );
3.5.3. Object Conversions

3.6. Arrays

3.6.1. Creating Arrays

var a = new Array( );
a[0] = 1.2;
a[1] = "JavaScript";
a[2] = true;
a[3] = { x:1, y:3 };
var a = new Array(1.2, "JavaScript", true, { x:1, y:3 });
var a = new Array(10);
var a = [1.2, "JavaScript", true, { x:1, y:3 }];

3.5.2. Object Literals

3.7. null

null is a special value that indicates no value

3.8. undefined

undefined is returned when you use either a variable that has been declared but never had a value assigned to it or an object property that does not exist. Note that this special undefined value is not the same as null.

3.9. The Date Object

3.12. Type Conversion Summary

Table 3-3. Automatic datatype conversions

Value

Context in which value is used

 

String

Number

Boolean

Object

Undefined value	"undefined"	NaN	false	Error
null	"null"	0	false	Error
Nonempty string	As is	Numeric value of string or NaN	TRue	String object
Empty string	As is	0	false	String object
0	"0"	As is	false	Number object
NaN	"NaN"	As is	false	Number object
Infinity	"Infinity"	As is	true	Number object
Negative infinity	"-Infinity"	As is	TRue	Number object
Any other number	String value of number	As is	true	Number object
true	"true"	1	As is	Boolean object
false	"false"	0	As is	Boolean object
Object	toString( )	valueOf( ), toString( ), or NaN	true	As is

 

covers advanced material

3.13. Primitive Datatype Wrapper Objects

3.14. Object-to-Primitive Conversion

3.15. By Value Versus by Reference

 

 

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