java script learning: Arrays object

Arrays:
It is a collection of elements of homogenious or different data types.

1. Creating Array

a) var n=[1,2,3,4,5];

var months[“Jan”, “Feb”, 3, 4, “May”];

b) var n=new array(1,2,3,4,5);

c) var n=new array[5];

2. Adding Elements : New element can be inserted at given position.

var n=[1,2,3,4,5];

var n[3]=6;

3. Accessing Elements

Last index is known by length attribute. So elements are accessed from beginning to

ending by using a loop.

Ex :

for(var i=0;i<ar.length;i++)

{

document.write(ar[i]);

}

Array indexes are zero-based, which means the first item is [0], second is [1], and so on.

Array Properties:

Here is a list of each property and their description.

Property	Description
constructor	Returns a reference to the array function that created the object.
index	The property represents the zero-based index of the match in the string
input	This property is only present in arrays created by regular expression matches.
length	Reflects the number of elements in an array.
prototype	The prototype property allows you to add properties and methods to an object.

Array Methods

Here is a list of each method and its description.

Method	Description
concat()	Returns a new array comprised of this array joined with other array(s) and/or value(s).
every()	Returns true if every element in this array satisfies the provided testing function.
filter()	Creates a new array with all of the elements of this array for which the provided filtering function returns true.
forEach()	Calls a function for each element in the array.
indexOf()	Returns the first (least) index of an element within the array equal to the specified value, or -1 if none is found.
join()	Joins all elements of an array into a string.
lastIndexOf()	Returns the last (greatest) index of an element within the array equal to the specified value, or -1 if none is found.
map()	Creates a new array with the results of calling a provided function on every element in this array.
pop()	Removes the last element from an array and returns that element.
push()	Adds one or more elements to the end of an array and returns the new length of the array.
reduce()	Apply a function simultaneously against two values of the array (from left-to-right) as to reduce it to a single value.
reduceRight()	Apply a function simultaneously against two values of the array (from right-to-left) as to reduce it to a single value.
reverse()	Reverses the order of the elements of an array -- the first becomes the last, and the last becomes the first.
shift()	Removes the first element from an array and returns that element.
slice()	Extracts a section of an array and returns a new array.
some()	Returns true if at least one element in this array satisfies the provided testing function.
toSource()	Represents the source code of an object
sort()	Sorts the elements of an array.
splice()	Adds and/or removes elements from an array.
toString()	Returns a string representing the array and its elements.
unshift()	Adds one or more elements to the front of an array and returns the new length of the array.

<!DOCTYPE html>

<html>

<body>

var i;//creating variable i of type number

var c = new Array();//array creatin

//var c = new Array[];// invalid due to [] brackets

/* array initialisation*/

c[0] = "idli";

c[1] = "wada";

c[2] = "dosa";

/* or we can initialise

var c=new Array("idli","wada","dosa");

(or)

var c=["idli","wada","dosa"];

for (i=0;i<c.length;i++)

{

document.write(c[i] + "<br>");

}

</script>

</body>

</html>

Examples

<html>

<head>

<title>accessing array elements</title>

</head>

<body>

// f=new Array(5);//creating array of size 5

/* f[0]="Rama";

f[1]="Sita";

f[2]="laxman";

f[3]="Bharat";

f[4]="Shathragna";*/

f=["Rama","Sita","laxman","Bharat","Shathragna",2,2.3,'m',true];//valid

//f={"Rama","Sita","laxman","Bharat","Shathragna"};//invalid

//var f=["Rama","Sita","laxman","Bharat","Shathragna"];//valid

//var f=("Rama","Sita","laxman","Bharat","Shathragna");//invalid

//printing array elements

var n=f.length;

for(var i=0;i<n;i++)

document.write(f[i]+"</br>");

var j=f.join();//this method is used to print array elements in a single line

// j=f.join();//VALID

document.write(j);

</script>

</body>

</html>

<!-Program for Array http://improvejavascript.blogspot.in/-->

<html>

<head>

var a=[1,2,3,4,5];

for(var i=0;i<a.length;i++)

document.writeln("<H1>"+a[i]+"</H1>");

</script>

</head>

<body>

</body>

</html>

<html>

<head>

<title>accessing array elements</title>

</head>

<body>

var f=new Array("Rama","Sita","laxman","Bharat","Shathragna",2,2.3,'m',true);

// var f=new array("Rama","Sita","laxman","Bharat","Shathragna",2,2.3,'m',true);////invalid due to small 'a'

//printing array elements

document.write(f[0]+"<br>");

document.write(f[1]+"<br>");

document.write(f[2]+"<br>");

document.write(f[3]+"<br>");

document.write(f[4]+"<br>");

j=f.join();//this method is used to print array elements in a single line

document.write(j);

</script>

</body>

</html>

ExAMPLE:

<! javascript array automatically extends its size-->

<html>

<head>

<title>accessing array elements</title>

</head>

<body>

var f=new Array(2);

//var f=new Array[2];//invalid due to [] brackes

f[0]="Rama";

f[1]=1//semicolon is optional

f[2]=3.2;

//printing array elements

document.write(f[0]+"<br>");

document.write(f[1]+"<br>");

document.write(f[2]+"<br>");

document.write(f[3]+"<br>");

document.write(f[4]+"<br>");

j=f.join();//this method is used to print array elements in a single line

document.write(j);

</script>

</body>

</html>

********************************************************************

<html>

<head>

<title>accessing array elements</title>

</head>

<body>

f=["Rama","Sita","laxman","Bharat","Shathragna",2,2.3,'m',true];//valid

// f=("Rama","Sita","laxman","Bharat","Shathragna");//invalid

//var f=["Rama","Sita","laxman","Bharat","Shathragna"];//valid

//var f=("Rama","Sita","laxman","Bharat","Shathragna");//invalid

//printing array elements

document.write(f[0]+"<br>");

document.write(f[1]+"<br>");

document.write(f[2]+"<br>");

document.write(f[3]+"<br>");

document.write(f[4]+"<br>");

j=f.join();//this method is used to print array elements in a single line

document.write(j);

</script>

</body>

</html>

Example: search an element and remove it from the array

<! searching an array-->

<html>

<head>

<title>searching a element</title>

</head>

<body>

var a=["Ram","kiran",34,36.54,"sita"];

// a=["Ram","kiran",34,36.54,'sita',"sita"];//valid

//display the array

document.writeln("<p>");

var n=a.length;

for(var i=0;i<n;i++)

{

document.write(a[i]+ " ,");

}

document.writeln("</p>");

//ask the user to remove item

var r=prompt("Please type what you want to remove"," ");

var temp=new Array(a.length-1);//we have to remove one element so -1 is must else we get "undefined"

var m=0;

//for loop searches, and removes

for(var i=0;i<n;i++)

{

if(a[i]==r)

{

//does nothing

;

}

else

{

temp[m]=a[i];

m++;

}

}//end of for loop

//copying from array temp to array a

a=temp;

//display the new array

document.write("<p>");

n=a.length;

for(var i=0;i<n;i++)

{

document.write(a[i]+" ,");

}

document.writeln("</p>");

// document.close();

</script>

</body>

</html>

// same program using external program
function search()
{

a=["Ram","kiran",34,36.54,'sita'];//valid
//display the array
document.writeln("<p>");
var n=a.length;
for(var i=0;i<n;i++)
{
document.write(a[i]+ " ,");

}
document.writeln("</p>");
//ask the user to remove item
var r=prompt("Please type what you want to remove"," ");
var temp=new Array(a.length-1);
var m=0;

//for loop searches, and removes
for(var i=0;i<n;i++)
{
if(a[i]==r)
{
//does nothing
;
}
else
{

temp[m]=a[i];
m++;
}
// document.writeln(r+ "Not found");
}//end of for loop
//copying from array temp to array a
a=temp;
//display the new array
document.write("<p>");
n=a.length;
for(var i=0;i<n;i++)
{
document.write(a[i]+" ,");
}
document.writeln("</p>");
//document.close();
}
//save the above program example SearchJs.js

<! searching an array-->
<html>
<head>
<title>searching a element</title>
<script type="text/JavaScript" src="SearchJs.js">
</script>
</head>
<body>
<input type="button" onclick="search()" value="remove"/>
</body>
</html>

Array Properties

rere

Property	Description
Constructor	Returns a reference to the array function that created the object

java script learning

Sunday 2 February 2014

Arrays object

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