Array Methods
Here is a list of the methods of the Array object along with their
description.
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Method
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Description
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concat()
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Returns
a new array
comprised of this
array
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joined with other array(s) and/or value(s).
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every()
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Returns
true if every
element in this
array
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satisfies the provided testing function.
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filter()
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Creates a new array with all of the elements
of
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this array for which the provided filtering
function
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returns true.
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forEach()
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Calls a function for each element in the
array.
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indexOf()
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Returns
the first (least)
index of an
element
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within the array equal to the specified
value, or -
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1 if none is found.
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join()
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Joins all elements of an array into a
string.
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lastIndexOf()
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Returns the last (greatest) index of an
element
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within the array equal to the specified
value, or -
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1 if none is found.
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map()
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Creates a new array with the results of
calling a
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provided function on every element in this
array.
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pop()
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Removes
the last element
from an array
and
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returns that element.
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push()
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Adds
one or more
elements to the
end of an
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array and returns the new length of the
array.
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reduce()
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Apply
a function simultaneously against
two
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values
of the array
(from left-to-right) as
to
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reduce it to a single value.
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reduceRight()
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Apply
a function simultaneously against
two
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values
of the array
(from right-to-left) as
to
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reduce it to a single value.
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reverse()
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Reverses the order of the elements of an
array --
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the first becomes the last, and the last
becomes
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the first.
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shift()
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Removes
the first element
from an array
and
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returns that element.
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slice()
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Extracts a section of an array and returns a
new
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array.
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some()
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Returns true if at least one element in this
array
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satisfies the provided testing function.
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toSource()
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Represents the source code of an object
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sort()
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Sorts the elements of an array.
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splice()
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Adds and/or removes elements from an array.
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toString()
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Returns a string representing the array and
its
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elements.
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unshift()
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Adds one or more elements to the front of an
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array and returns the new length of the
array.
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In the following
sections, we will have a few examples to demonstrate the usage of Array
methods.
concat ()
Javascript array concat() method returns a new array comprised of this array joined
with two or more arrays.
Syntax
The syntax of concat() method is as follows:
array.concat(value1, value2, ..., valueN);
Parameter Details
valueN : Arrays and/or values to concatenate to the
resulting array.
Return Value
Returns the length of the array.
Example
Try the following example.
<html>
<head>
<title>JavaScript Array concat
Method</title>
</head>
<body>
<script
type="text/javascript">
var alpha = ["a", "b",
"c"];
var numeric = [1, 2, 3];
var alphaNumeric =
alpha.concat(numeric); document.write("alphaNumeric : " +
alphaNumeric );
</script>
</body>
</html>
Output
alphaNumeric : a,b,c,1,2,3
every ()
Javascript array every method tests whether all the elements in an array passes the
test implemented by the provided function.
Syntax
Its syntax is as follows:
array.every(callback[, thisObject]);
Parameter Details
·
callback : Function to test for each element.
·
thisObject : Object to use as this when
executing callback.
Return Value
Returns true if every element in this array satisfies the provided
testing function.
Compatibility
This method is a
JavaScript extension to the ECMA-262 standard; as such it may not be present in
other implementations of the standard. To make it work, you need to add the
following code at the top of your script.
if (!Array.prototype.every)
{
Array.prototype.every = function(fun /*,
thisp*/)
{
var len = this.length;
if (typeof fun != "function")
throw new TypeError();
var thisp = arguments[1];
for (var i = 0; i < len; i++)
{
if (i in this &&
!fun.call(thisp, this[i], i, this))
return false;
}
return true;
};
}
Example
Try the following example.
<html>
<head>
<title>JavaScript Array every
Method</title>
</head>
<body>
<script
type="text/javascript">
if (!Array.prototype.every)
{
Array.prototype.every = function(fun /*,
thisp*/)
{
var len = this.length;
if (typeof fun != "function")
throw new TypeError();
var thisp = arguments[1];
for (var i = 0; i < len; i++)
{
if (i in this &&
!fun.call(thisp, this[i], i, this))
return false;
}
return true;
};
}
function
isBigEnough(element, index, array) { return (element >= 10);
}
var passed = [12, 5, 8, 130,
44].every(isBigEnough); document.write("First Test Value : " + passed
);
passed = [12, 54, 18, 130,
44].every(isBigEnough);
document.write("Second Test Value :
" + passed );
</script>
</body>
</html>
Output
First Test Value : falseSecond Test Value :
true
filter ()
Javascript array filter() method creates a new array with all elements that pass the
test implemented by the provided function.
Syntax
Its syntax is as follows:
array.filter (callback[, thisObject]);
Parameter Details
·
callback : Function to test for each element of an array.
·
thisObject : Object to use as this when
executing callback.
Return Value
Returns created array.
Compatibility
This method is a
JavaScript extension to the ECMA-262 standard; as such it may not be present in
other implementations of the standard. To make it work, you need to add the
following code at the top of your script.
if (!Array.prototype.filter)
{
Array.prototype.filter = function(fun /*,
thisp*/)
{
var len = this.length;
if (typeof fun != "function")
throw new TypeError();
var res = new Array();
var thisp = arguments[1];
for (var i = 0; i < len; i++)
{
if (i in this)
{
var val = this[i]; // in case fun
mutates this if (fun.call(thisp, val, i, this))
res.push(val);
}
}
return res;
};
}
Example
Try the following example.
<html>
<head>
<title>JavaScript Array filter
Method</title>
</head>
<body>
<script
type="text/javascript">
if (!Array.prototype.filter)
{
Array.prototype.filter = function(fun /*,
thisp*/)
{
var len = this.length;
if (typeof fun != "function")
throw new TypeError();
var res = new Array();
var thisp = arguments[1];
for (var i = 0; i < len; i++)
{
if (i in this)
{
var val = this[i]; // in case fun
mutates this if (fun.call(thisp, val, i, this))
res.push(val);
}
}
return res;
};
}
function
isBigEnough(element, index, array) { return (element >= 10);
}
var filtered = [12, 5, 8, 130,
44].filter(isBigEnough); document.write("Filtered Value : " +
filtered );
</script>
</body>
</html>
Output
Filtered Value : 12,130,44
forEach ()
Javascript array forEach() method calls a function for each element in the array.
Syntax
Its syntax is as follows:
array.forEach(callback[, thisObject]);
Parameter Details
·
callback : Function to test for each element of an array.
·
thisObject : Object to use as this when executing callback.
Return Value
Returns the created array.
Compatibility
This method is a
JavaScript extension to the ECMA-262 standard; as such it may not be present in
other implementations of the standard. To make it work, you need to add
following code at the top of your script.
if (!Array.prototype.forEach)
{
Array.prototype.forEach = function(fun /*,
thisp*/)
{
var len = this.length;
if (typeof fun != "function")
throw new TypeError();
var thisp = arguments[1];
for (var i = 0; i < len; i++)
{
if (i in this)
fun.call(thisp, this[i], i, this);
}
};
}
Example
Try the following example.
<html>
<head>
<title>JavaScript Array forEach
Method</title>
</head>
<body>
<script
type="text/javascript">
if (!Array.prototype.forEach)
{
Array.prototype.forEach = function(fun /*,
thisp*/)
{
var len = this.length;
if (typeof fun != "function")
throw new TypeError();
var thisp = arguments[1];
for (var i = 0; i < len; i++)
{
if (i in this)
fun.call(thisp, this[i], i, this);
}
};
}
function
printBr(element, index, array) { document.write("<br />[" +
index + "] is " + element );
}
[12, 5, 8, 130, 44].forEach(printBr);
</script>
</body>
</html>
Output
[0] is 12
[1] is 5
[2] is 8
[3] is 130
[4] is 44
indexOf ()
Javascript array indexOf() method returns the first index at which a given element
can be found in the array, or -1 if it is not present.
Syntax
Its syntax is as follows:
array.indexOf(searchElement[, fromIndex]);
Parameter Details
·
searchElement : Element to locate in the array.
·
fromIndex : The index at which to
begin the search. Defaults to 0, i.e. the
whole array will be searched. If the index is greater than or equal to the
length of the array, -1 is returned.
Return Value
Returns the index of the found element.
Compatibility
This method is a
JavaScript extension to the ECMA-262 standard; as such it may not be present in
other implementations of the standard. To make it work, you need to add the
following code at the top of your script.
if (!Array.prototype.indexOf)
{
Array.prototype.indexOf = function(elt /*,
from*/)
{
var len = this.length;
var from = Number(arguments[1]) || 0;
from = (from < 0)
? Math.ceil(from)
: Math.floor(from);
if (from < 0)
from += len;
for (; from < len; from++)
{
if (from in this &&
this[from] === elt)
return from;
}
return -1;
};
}
Example
Try the following example.
<html>
<head>
<title>JavaScript Array indexOf
Method</title>
</head>
<body>
<script
type="text/javascript">
if (!Array.prototype.indexOf)
{
Array.prototype.indexOf = function(elt /*,
from*/)
{
var len = this.length;
var from = Number(arguments[1]) || 0;
from = (from < 0)
? Math.ceil(from)
: Math.floor(from); if (from < 0)
from += len;
for (; from < len; from++)
{
if (from in this &&
this[from] === elt)
return from;
}
return -1;
};
}
function printBr(element,
index, array) { document.write("<br />[" + index + "] is
" + element );
}
var index = [12, 5, 8, 130,
44].indexOf(8); document.write("index is : " + index );
var index = [12, 5, 8, 130, 44].indexOf(13);
document.write("<br />index is :
" + index );
</script>
</body>
</html>
Output
index is : 2
index is : -1
join ()
Javascript array join()
method joins all the elements of an array into a string.
Syntax
Its syntax is as follows:
array.join(separator);
Parameter Details
separator
:
Specifies a string to separate each element of the array. If omitted, the array elements are separated with
a comma.
Return Value
Returns a string after joining all the array elements.
Example
Try the following example.
<html>
<head>
<title>JavaScript Array join
Method</title>
</head>
<body>
<script
type="text/javascript">
var arr = new
Array("First","Second","Third");
var str = arr.join();
document.write("str : " + str );
var str = arr.join(", ");
document.write("<br />str : " + str );
var str = arr.join(" + ");
document.write("<br />str : "
+ str );
</script>
</body>
</html>
Output
str : First,Second,Third
str : First, Second, Third
str : First + Second + Third
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