Question

How to use Array.reduce() and function to sum array values in JavaScript

Answer 1

var arr = [1, 2, 3, 4]

var arr_reduce = arr.reduce(function(previousValue, currentValue, currentIndex, array) {
  return previousValue + currentValue;
});

console.log(arr_reduce); 
 
 
/*
run:  
  
10
   
*/

 

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Answer 2

var arr = [1, 2, 3, 4, 5]

var arr_reduce = arr.reduce( (prev, curr) => prev + curr );

console.log(arr_reduce); 
 
 
/*
run:  
  
15
   
*/

 

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Answer 3

var arr = [1, 2, 3, 4, 5]

var arr_reduce = arr.reduce(function(previousValue, currentValue, currentIndex, array) {
  return previousValue + currentValue;
}, 100);

// 100 initial value to sum (100 + 1 + 2 + 3 + 4 + 5)

console.log(arr_reduce); 
 
 
/*
run:  
  
115
   
*/

 

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Answer 4

var arr = [1, 2, 3, 4, 5]

var sum = arr.reduce(function(a, b) {
  return a + b;
});

console.log(sum); 
 
 
/*
run:  
  
15
   
*/

 

70+ SQL courses for beginners and professionals