Undefined array parameter with Javascript

Question

I can't see why this function is returning undefined:

function sumArray(array) {
  array.reduce(function(result, item) {
    return result + item;
  })
}

array = [1,2,3]

sumArray(array)

I've tried something similar and it works ok (below), so I'm not sure if it's specific to the parameter being an array?

function sayNumber(num) {
 return num + 1;
} 

num = 1

sayNumber(num)

Any function that doesn't explicitly return something returns "undefined" instead. You just invoke the array.reduce method but your not returning it so it really doesn't have anything to return — Chris
– Chris, Commented Oct 29, 2017 at 14:05

Ivan Kalita · Accepted Answer · 2017-10-29 14:04:26Z

2

What you actually need is to add one more return statement.

function sumArray(array) {
  //here
  return array.reduce(function(result, item) {
    return result + item;
  });
}

array = [1,2,3];

sumArray(array);
//6

answered Oct 29, 2017 at 14:04

Ivan Kalita

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1 Comment

Ivan Kalita Over a year ago

@safikabis, happy to help and welcome to Stack Overflow! If this or any other answer solved your problem, please, mark it as accepted.

glaand · Accepted Answer · 2017-10-29 14:04:43Z

0

The function sumArray is not returning the result from array.reduce. Insert a return before your array.reduce.

answered Oct 29, 2017 at 14:04

glaand

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Comments

Quentin · Accepted Answer · 2017-10-29 14:04:53Z

0

It returns undefined because there is no return statement for the sumArray function.

(The anonymous function you pass to reduce has one, but that is a different function).

If you want to return the result of calling array.reduce when you have to say so explicitly:

return array.reduce(etc, etc…

answered Oct 29, 2017 at 14:04

Quentin

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Comments

James Pham · Accepted Answer · 2017-10-29 14:09:14Z

0

You should return the value of the function sumArray Like this:

function sumArray(array) {
  return array.reduce(function(result, item) {
    return result + item;
  })
}

answered Oct 29, 2017 at 14:09

James Pham

1

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