Core JavaScript

Array, Boolean, Date, Function, Math, Number, Object, String, regExp

Core JavaScript

Array

The Array object let's you store multiple values in a single variable.

Syntax:

var leaders = new Array( “Gandhi",

“Mandela",

“Aung San Suu Kyi " ); or

var fruits = [ “Gandhi", “Mandela", “Aung San Suu Kyi “ ];

leaders[0]=Gandhileaders[1]=Mandelaleaders[2]=Aung San Suu Kyi

August 26 1988, addressed a half-million mass rally in front of the famous Shwedagon Pagoda in Rangoon

Purpose: call for a democratic government.

Military Govt arrest: detained for six years and released on July 10, 1995. During detention was awarded the 1991 Nobel Peace Prize.

Established a health and education trust in support of the Burmese people to use the $1.3 million prize money.

Quotes:A good head and a good

heart are always a formidable combination.

Education is the most powerful weapon which you can use to change the world.

Array PropertiesProperty Description

constructor Returns a reference to the array function that created the object.

length Reflects the number of elements in an array.

prototypeThe prototype property allows you to add properties and methods to an object.

array_nm.length

<body> <script type="text/javascript">

var arr = new Array( 10, 20, 30 ); document.write("arr.length is : " + arr.length); </script>

</body>

Output: arr.length is : 3

Property : Constructor

<html> <head> <title> JavaScript Array constructor Property</title> </head>

<body> <script type="text/javascript"> var arr = new Array( 10, 20, 30 ); document.write("arr.constructor is::" + arr.constructor); </script> </body> </html>

arr.constructor is:: function Array() { [native code] }

Property: PrototypeThe prototype property allows you to add properties

and methods to any object (Number, Boolean, String and Date etc).

Note: Prototype is a global property which is available with almost all the objects.

Syntax:object.prototype.name = value

Prototype Example…

<html> <head> <title>User-defined

objects</title> <script type="text/javascript"> function book(title, author) { this.title = title; this.author = author; } </script> </head>

<body> <script type="text/javascript"> var myBook = new book(“linux", “Oreilly"); book.prototype.price = null; myBook.price = 100;

document.write("Book title is : " + myBook.title + "<br>"); document.write("Book author is : " + myBook.author + "<br>"); document.write("Book price is : " + myBook.price + "<br>"); </script> </body> </html>

Book title is : linuxBook author is : OreillyBook price is : 100

Array MethodsMethod Description

sort() Sorts the elements of the array

concat() returns a new array comprised of this array joined with two or more arrays.

indexOf() Returns the location of the element position

lastIndexOf() Search the array for an element, starting at the end, and returns it's position

reverse() reverses the order of the elements in an array.

Push() Adds new elements to the end of an array, and returns the new length

Pop() Removes the last element of an array, and returns that element

unshift() Adds new elements to the beginning of an array, and returns the new length

Shift() Removes the first element of an array, and returns that element

array_name.sort()<script type="text/javascript"> </script>

Aung SanGandhiMandela

Array_nm.reverse()var fruits = ["Banana", "Orange", "Apple", "Mango"];

fruits.reverse();

The result of fruits will be:Mango,Apple,Orange,Banana

array_name.concat()1. <script type="text/javascript">

2. var alpha = ["a", "b", "c"];

3. var numeric = [1, 2, 3];

4. var alphaNumeric = alpha.concat ( numeric );

5. document.write("alphaNumeric : " + alphaNumeric );

6. </script>

alphaNumeric : a,b,c,1,2,3

1. <script type="text/javascript">

2. var alpha = ["a", "b", "c"];

3. var numeric = [1, 2, 3];

4. var symbols = [“%”,”$”, “#”];

5. var alphaNumeric = alpha.concat ( numeric, symbols );

6. document.write("alphaNumeric : " + alphaNumeric );

7. </script>

array_name.concat()

alphaNumeric : a,b,c,1,2,3,%,$,#

Practice QuestionCreate 2 arrays: leaders {Gandhi, Mandela, Aung San}Countries {India, Burma, S.Africa}

Write a JavaScript to concatenate and sort the two arrays:

Such that the output is as follows:

sortNconcat:

Aung San, Burma, Gandhi, India, Mandela, S.Africa

List two any 2 ways to perform the above task.

Key:<script type="text/javascript"> </script

array_name.indexOf()

What does it do?The indexOf() method searches the array for the specified

item, and returns it's position.

How does it search?The search will start at the specified position, or at the

beginning if no start position is specified, and end the search at the end of the array.

What if it does not find the element?It Returns -1 if the item is not found.

If duplicate entries exist then?Then indexOf method returns the position of the first

occurrence.

What if the element is on the first position?The first item has position 0, the second item has

position 1, and so on. So indexOf() would return 0.

What if we wish to search from back to front?If you want to search from end to start, use the

lastIndexOf() method

The indexOf() method is not supported in Internet Explorer 8 and earlier as it was introduces in javascript 1.6.

http://www.w3schools.com/jsref/jsref_lastindexof_array.asp

Syntax: array.indexOf(item,start)

Parameter Description

item Required. The item to search for

startOptional. Where to start the search. Negative values will start at the given position counting from the end, and search to the end.

var fruits = [ "Banana", "Orange", "Apple", "Mango", "Banana", "Orange", "Apple"];

var a = fruits.indexOf("Apple",4);

The result of a will be: 6

Array_nm.lastIndexOf(item,start)The lastIndexOf() method searches the array for the

specified item, and returns it's position.

The search will start at the specified position, or at the end if no start position is specified, and end the search at the beginning of the array.

Returns -1 if the item is not found.

If the item to search for is present more than once, the lastIndexOf method returns the position of the last occurence.

Example 1: LastIndexOf(item,start);

var fruits = ["Banana", "Orange", "Apple", "Mango"];

var a = fruits.lastIndexOf("Apple");


Example 2 : LastIndexOf(item,start);

var fruits = [ "Banana", "Orange", "Apple", "Mango", "Banana", "Orange", "Apple", "Mango“ ];

var a=fruits.lastIndexOf("Apple",4)


Example 3 : LastIndexOf(item,start);

var fruits = [ "Banana", "Orange", "Apple", "Mango", "Banana", "Orange", "Apple", "Mango“ ];

var a=fruits.lastIndexOf("Apple",7)


Array_name.push()The push() method adds new items to the end of an

array, and returns the new length.

The new item(s) will be added at the end of the array.

This method changes the length of the array.

Tip: To add items at the beginning of an array, use the unshift() method.

Example:var fruits = ["Banana", "Orange", "Apple", "Mango"];

fruits.push("Kiwi")

The result of fruits will be:

Banana,Orange,Apple,Mango,Kiwi

In order to add more items, use the comma separator and pass as arguments.

Unshift()array.unshift(item1,item2, ..., itemX);

var fruits = ["Banana", "Orange", "Apple", "Mango"];

fruits.unshift("Lemon","Pineapple");

Output:The result of fruits will be:Lemon,Pineapple,Banana,Orange,Apple,Mango

Shift()Syntax: array.shift()

The shift() method removes the first item of an array, and returns that item.

Remember:This method changes the length of an array!

Trick: To remove the last item of an array, use the pop() method

Example:var fruits = ["Banana", "Orange", "Apple", "Mango"];

fruits.shift()

OUTPUT:The result of fruits will be:Orange, Apple, Mango

There exist 14 methods in all for the array object

Strings:The String object is used to manipulate a stored piece

of text.

String objects are created with new String().

Syntax:var txt = new String("string"); var txt = "string";

Search()The search() method searches a string for a specified

value, or regular expression, and returns the position of the match.

This method returns -1 if no match is found.

Syntax:string.search(searchvalue)

Str_nm.search(searchValue)

Parameter: Parameter Description searchvalue Required.

Value: The value, or regular expression, to search for.

Return Valueposition of the first occurance of the specified

searchvalue

Example: search()var str= “Tina Ma’am stays at Colaba";

document.write(str.search(“at"));

The result of n will be?18171615

Think Think Think What is the difference between indexOf()

and search() methods for a string, if they perform the same task???

Substr()

This method returns the characters in a string beginning at the specified location through the specified number of characters.

Syntax:string.substr(start[, length]);

start : Location at which to begin extracting characters (an integer between 0 and one less than the length of the string).

length : The number of characters to extract.

Substr()Note: If start is negative, substr uses it as a

character index from the end of the string.

The substr method returns the new sub string based on given parameters.

Watch out for the next interesting program:

<html> <head> <title>JavaScript String substr() Method</title>

</head> <body> <script type="text/javascript">

var str = "Apples are round, and apples are juicy."; document.write("(1,2): " + str.substr(1,2)); document.write("<br />(-2,2): " + str.substr(-2,2)); document.write("<br />(1): " + str.substr(1)); document.write("<br />(-20, 2): " + str.substr(-20,2)); document.write("<br />(20, 2): " + str.substr(20,2)); </script> </body> </html>

Now jot down your answers

(1,2): pp (-2,2): Ap (1): pples are round, and apples are juicy. (-20, 2): Ap (20, 2): d

Core JavaScript

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