JavaScript Array method: reduce()
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The reduce() method (when applied to a JavaScript
array) reduces
the values of an array to a single value (from left to right, i.e. from lowest
to highest index).
It
has the following syntax with the following parameters. It returns the
accumulated result from the last call of the function. It does not execute the
function if the array element does not have a value.
array.reduce(function(total, currentValue,
index, arr), initialValue)
|
Parameter
|
Required / Optional
|
Description
|
|
function(total,
currentValue, index, arr)
|
Required
|
A function to be run
for each element
|
|
initialValue
|
Optional
|
A value to be passed to
the function to be used as the initial value
|
The function
arguments are:
|
Parameter
|
Required / Optional
|
Description
|
|
total
|
Required
|
The initalValue
or the previously returned value of the function
|
|
currentValue
|
Required
|
The value of the
current element
|
|
Index
|
Optional
|
The array index of the
current element
|
|
arr
|
Optional
|
The array object which
the current element belongs to
|
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