It is just
like reduce, instead of combinig elements from left to right, it combine
elements from right to left.
Syntax
arr.reduceRight(callback[,
initialValue])
callback
function takes four arguments.
Argument
|
Description
|
previousValue
|
The
value previously returned in the last invocation of the callback, or
initialValue, if supplied.
|
currentValue
|
The
current element being processed in the array.
|
currentIndex
|
The
index of the current element being processed in the array. Starts at index 0,
if an initialValue is provided, and at index 1 otherwise.
|
array
|
The
array reduceRight was called upon.
|
initialValue
It is
optional, Value to use as the first argument to the first call of the callback.
function
add(x, y){
return x+y;
}
var
sumOfEle = arr1. reduceRight(add, 0);
Above
statements are used to calculate sum of elements of the array.
function
mul(x, y){
return x*y;
}
var
mulOfEle = arr1.reduceRight(mul, 1);
Above
statements are used to compute multiplication of elements in array.
function
max(x, y){
return ((x>y)?x:y);
}
var
maximum = arr1. reduceRight(max);
Above
statements are used to compute maximum value in the array.
reduceRight.html
<!DOCTYPE html> <html> <head> <title>Array reduceRight example</title> </head> <body> <script type="text/javascript"> var arr1 = [12, 43, 2, 3, 98, 6]; function add(x, y) { return x + y; } function mul(x, y) { return x * y; } function max(x, y) { return ((x > y) ? x : y); } var sumOfEle = arr1.reduceRight(add, 0); var mulOfEle = arr1.reduceRight(mul, 1); var maximum = arr1.reduceRight(max); document.write("Sum of elements in array is " + sumOfEle + "<br />"); document.write("Multiplication of elements in array is " + mulOfEle + "<br />"); document.write("Maximum number in array is " + maximum + "<br />"); </script> </body> </html>
Open above
page in browser, you can able to see following text.
Sum of
elements in array is 164
Multiplication
of elements in array is 1820448
Maximum
number in array is 98
JavaScript: Arrays: indexOf: Get the
index of first occurrence of element
‘indexOf’
method is used to get the the index of first occurrence of the element. Return
the index if the element is found, else -1.
Syntax
arr.indexOf(searchElement[,
fromIndex = 0])
If the fromIndex
value is a negative number, it is taken as the offset from the end of the
array.
Argument
|
Description
|
searchElement
|
Element
to search
|
fromIndex
|
The
index to start the search at.
|
indexOf.html
<!DOCTYPE html> <html> <head> <title>indexOf example</title> </head> <body> <script type="text/javascript"> var arr = [2, 3, 5, 7, 2, 3, 2, 5]; document.write("index of first occurrence of element 2 " + arr.indexOf(2) + "<br />"); document.write("index of occurrence of element 2 from index 5 " + arr.indexOf(2, 5) + "<br />"); document.write("index of occurrence of element 2 from index 7 " + arr.indexOf(2, 7) + "<br />"); </script> </body> </html>
Open above
page in browser, you can able to see following text.
index of
first occurrence of element 2 0
index of
occurrence of element 2 from index 5 6
index of
occurrence of element 2 from index 7 -1
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