Javascript Reference - How to reduce a Javascript array from the end

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reduceRight() is reduction method. reduceRight() iterates all items and build up a value for return. reduceRight() starts at the last and travels toward the first.

reduceRight() accepts two arguments.

• a function to call on each item
• an optional initial value

The function passed into reduceRight() accepts four arguments.

• the previous value,
• the current value,
• the item's index,
• the array object.

The returned value from the function is passed in as the first argument for the next item. The first iteration occurs on the second item in the array.

The reduceRight() method works in the same way, just in the opposite direction.

Example

var values = [1,2,3,4,5]; 
        
var sum = values.reduceRight(function(prev, cur, index, array){
  return prev + cur; 
}); 
        
console.log(sum); //15 

The code above generates the following result.

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