Javascript Reference Card (Page 4 of 6) in pdf

Initializing Arrays:

WHILE LOOP:

Array items can be treated as simple variables:

Format:

days[0] = “Sunday”;

while (condition) {

days[1] = “Monday”;

Statements;

etc.

Increment/decrement;

}

STRING OBJECT

Example:

Definition: String object is created by assigning a string to a

var i = 0;

variable, or by using the new object constructor.

while (i<=10)

{

Example:

document.write (“This is line “ + i);

i++;

var name = “Carol”;

}

var name = new String(“Carol”);

Hint: Watch out for infinite loops, which do not have a

Properties:

stopping condition or have a stopping condition that will

returns the number of characters in the

Length:

never be reached.

string

allows the user to add methods and

Prototype:

OBJECTS

properties to the string

Methods:

Definition: Objects are a composite data type which con-

String formatting methods (similar to HTML formatting tags)

tain properties and methods. JavaScript contains built-in

String.big

objects and allows the user to create custom objects.

String.blink

Creating Objects: Use the new constructor

String.italics

var X = new Array()

Substring methods (allow user to find, match, or change

Examples:

patterns of characters in the string)

date, time, math, strings, arrays

indexOf()

charAt()

ARRAY OBJECT

replace()

Definition: Array object is a variable that stores multiple val-

MATH OBJECT

ues. Each value is given an index number in the array and

Definition: Math object allows arithmetic calculations not

each value is referred to by the array name and the

supported by the basic math operators. Math is a built-in

index number. Arrays, like simple variables, can hold any

object that the user does not need to define.

kind of data. You can leave the size blank when you create

an array. The size of the array will be determined by the

Examples:

number of items placed in it.

returns absolute value of

Math.abs(number)

Format:

the numeric argument

var arrayname = new Array(size)

returns the cosine of the

Math.cos(number)

argument, in radians

Hint: When you create an array, you create a new instance

of the array object. All properties and methods of the array

rounds number to the

Math.round(number)

object are available to your new array.

nearest integer

Example:

DATE/TIME OBJECTS

var days = new Array (7)

Date object provides methods for getting or setting infor-

This creates an array of seven elements using the array

mation about the date and time.

constructor.

Note: Dates before January 1, 1970 are not supported.

The first item is days[0], the last item is days[6].

Javascript Reference Card Page 4

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