JavaScript TypedArray reduce() Method

The JavaScript reduce() method reduces the elements of an array into a single value and the returned value of the function is stored in an accumulator and each element in the array (from left to right) has to reduce it to a single value.

Note: Calling reduce() on an empty array without an initial value is an error.

Syntax:

Parameters:

Total(required): The previously returned value of the function.

CurrentValue(Required): The value of the current element.

Index(Optional): The index of the current element being processed in the array. Starts at index 0.

Arr(Optional): The array reduce() was called upon.

InitialValue(Optional): A value to be passed to the function as the initial value.

Return value:

Return the reduced single value of the array.

Browser Support:

Chrome	Yes
Safari	4
Firefox	3.0
Opera	10.5

Example 1

JavaScript reduce() Method

<script type="text/javascript">
// JavaScript to illustrate reduce() method
let JavaTpoint =[10,20,30];
// find the sum of all the elements 
let sum = JavaTpoint.reduce(function(passedIn, item)
{
return passedIn + item;
// 0 is intial value 
},0); 
document.write('Array sum is ',sum,'\n');
// expected output: JavaTpoint [Output: 60] 

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Output:

Example 2

JavaScript reduce(initialValue) Method

<script type="text/javascript">
// JavaScript to illustrate reduce() method
let JavaTpoint =[10,20,30];
// find the sum of all the elements 
let sum=JavaTpoint.reduce(function(passedIn, item)
{
return passedIn + item;
// 5 is intial value 
},5); 
document.write('Array sum is ',sum,'\n');
// expected output: JavaTpoint [Output: 65]    
</script>

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Output:

Example 3

JavaScript reduce() Method

<script>
// JavaScript to illustrate reduce() method
// Taking some array as the element of an array "A"
var A = [ ['Java','MongoDB' ], ['python','C'], [ 'RDBMS', 'C++' ] ];
// Calling array.reduce() function
a = A.reduce((previousValue, currentValue) => previousValue.concat(currentValue));
// printing result
document.write(a);
// expected output: Java,MongoDB,python,C,RDBMS,C++
</script>

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Output: