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Array methods - reverse (), shift (), slice (), some (), sort (), splice (), toString (), unshift () in javascript with syntax - Tech-n-Savvy Blogger


reverse ()

JavaScript array reverse() method reverses the element of an array. The first array element becomes the last and the last becomes the first.

Syntax

Its syntax is as follows:

array.reverse();

Return Value

Returns the reversed single value of the array.



Example

Try the following example.

<html>

<head>

<title>JavaScript Array reverse Method</title>

</head>
<body>

<script type="text/javascript">

var arr = [0, 1, 2, 3].reverse();

document.write("Reversed array is : " + arr );

</script>

</body>

</html>

Output

Reversed array is : 3,2,1,0


shift ()

Javascript array shift() method removes the first element from an array and returns that element.

Syntax

Its syntax is as follows:

array.shift();

Return Value

Returns the removed single value of the array.

Example

Try the following example.

<html>

<head>

<title>JavaScript Array shift Method</title>

</head>

<body>

<script type="text/javascript">

var element = [105, 1, 2, 3].shift(); document.write("Removed element is : " + element );

</script>

</body>

</html>

Output

Removed element is : 105


slice ()

Javascript array slice() method extracts a section of an array and returns a new array.

Syntax

Its syntax is as follows:

array.slice( begin [,end] );

Parameter Details

·         begin : Zero-based index at which to begin extraction. As a negative index, start indicates an offset from the end of the sequence.

·         end : Zero-based index at which to end extraction.

Return Value

Returns the extracted array based on the passed parameters.

Example

Try the following example.

<html>

<head>

<title>JavaScript Array slice Method</title>

</head>

<body>

<script type="text/javascript">

var arr = ["orange", "mango", "banana", "sugar", "tea"]; document.write("arr.slice( 1, 2) : " + arr.slice( 1, 2) ); document.write("<br />arr.slice( 1, 2) : " + arr.slice( 1, 3) );

</script>

</body>

</html>

Output

arr.slice( 1, 2) : mango

arr.slice( 1, 2) : mango,banana


some ()

Javascript array some() method tests whether some element in the array passes the test implemented by the provided function.

Syntax

Its syntax is as follows:

array.some(callback[, thisObject]);

Parameter Details

·         callback : Function to test for each element.

·         thisObject : Object to use as this when executing callback.

Return Value

If some element pass the test, then it returns true, otherwise false.

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.some)

{

Array.prototype.some = 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 true;

}


return false;

};

}

Example

Try the following example.

<html>

<head>

<title>JavaScript Array some Method</title>

</head>

<body>

<script type="text/javascript">

if (!Array.prototype.some)

{

Array.prototype.some = 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 true;

}

return false;

};

}


function isBigEnough(element, index, array) {

return (element >= 10);

}


var retval = [2, 5, 8, 1, 4].some(isBigEnough); document.write("Returned value is : " + retval );


var retval = [12, 5, 8, 1, 4].some(isBigEnough);

document.write("<br />Returned value is : " + retval );

</script>

</body>

</html>

Output

Returned value is : false

Returned value is : true


sort ()

Javascript array sort() method sorts the elements of an array.

Syntax

Its syntax is as follows:

array.sort( compareFunction );

Parameter Details

compareFunction: Specifies a function that defines the sort order. If omitted, the array is sorted lexicographically.



Return Value

Returns a sorted array.

Example

Try the following example.

<html>

<head>

<title>JavaScript Array sort Method</title>

</head>

<body>

<script type="text/javascript">

var arr = new Array("orange", "mango", "banana", "sugar");


var sorted = arr.sort();

document.write("Returned string is : " + sorted );


</script>

</body>

</html>

Output

Returned string is : banana,mango,orange,sugar


splice ()

Javascript array splice() method changes the content of an array, adding new elements while removing old elements.

Syntax

Its syntax is as follows:

array.splice(index, howMany, [element1][, ..., elementN]);

Parameter Details

·         index: Index at which to start changing the array.

·         howMany: An integer indicating the number of old array elements to remove. If howMany is 0, no elements are removed.

·         element1, ..., elementN: The elements to add to the array. If you don't specify any elements, splice simply removes the elements from the array.

Return Value

Returns the extracted array based on the passed parameters.

Example

Try the following example.

<html>

<head>

<title>JavaScript Array splice Method</title>

</head>

<body>

<script type="text/javascript">

var arr = ["orange", "mango", "banana", "sugar", "tea"];


var removed = arr.splice(2, 0, "water"); document.write("After adding 1: " + arr ); document.write("<br />removed is: " + removed);


removed = arr.splice(3, 1);

document.write("<br />After adding 1: " + arr );

document.write("<br />removed is: " + removed);


</script>

</body>

</html>

Output

After adding 1: orange,mango,water,banana,sugar,tea removed is:

After adding 1: orange,mango,water,sugar,tea

removed is: banana


toString ()

Javascript array toString() method returns a string representing the source code of the specified array and its elements.

Syntax

Its syntax is as follows:

array.toString( );

Return Value

Returns a string representing the array.

Example

Try the following example.

<html>

<head>

<title>JavaScript Array toString Method</title>

</head>

<body>

<script type="text/javascript">

var arr = new Array("orange", "mango", "banana", "sugar");


var str = arr.toString(); document.write("Returned string is : " + str );


</script>

</body>

</html>

Output

Returned string is : orange,mango,banana,sugar


unshift ()

Javascript array unshift() method adds one or more elements to the beginning of an array and returns the new length of the array.


Syntax

Its syntax is as follows:

array.unshift( element1, ..., elementN );

Parameter Details

element1, ..., elementN : The elements to add to the front of the array.

Return Value

Returns the length of the new array. It returns undefined in IE browser.

Example

Try the following example.

<html>

<head>

<title>JavaScript Array unshift Method</title>

</head>

<body>

<script type="text/javascript">

var arr = new Array("orange", "mango", "banana", "sugar");


var length = arr.unshift("water"); document.write("Returned array is : " + arr ); document.write("<br /> Length of the array is : " + length );


</script>

</body>

</html>

Output

Returned array is : water,orange,mango,banana,sugar

Length of the array is : 5


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