Getting undefined when using function

Question

I'm trying to write a function that used reduce() method to count the number of items in an array and return the length of that array.

This is what I have so far:

function len(items) {
    items.reduce(function(prev, curr, index){
        return index+1;
    });
}

let nums = [1, 2, 3];

console.log(len(nums));

Whenever I try to run this code, in the console on my browser I get the message 'undefined'. I think I defined my function properly, so I don't know why its not being called or outputting any values. Please let me know what I'm doing wrong or if my logic is wrong.

gurvinder372 · Accepted Answer · 2016-10-07 06:18:53Z

2

You forgot to return

function len(items) {
    return items.reduce(function(prev, curr, index){
        return index+1;
    });
}

or simply

function len(items) {
    return items.length;
}

answered Oct 7, 2016 at 6:18

gurvinder372

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2 Comments

FlameDra Over a year ago

I need to use reduce in order to get the length.

gurvinder372 Over a year ago

@flamedra then you can choose first option I have mentioned.

A.T. · Accepted Answer · 2016-10-07 06:19:03Z

2

function len(items) {
    return items.reduce(function(prev, curr, index){
        return index+1;
    });
}

let nums = [1, 2, 3];

console.log(len(nums));

answered Oct 7, 2016 at 6:19

A.T.

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1 Comment

FlameDra Over a year ago

This is working. Can you please explain whey I need to return both the reduce method when I'm also returning inside the function?

Nitya Kumar · Accepted Answer · 2016-10-07 06:22:56Z

0

try this :

function len(items) {
  if(items){                 //error handle
    return items.length;

  }
       return 0;
}

answered Oct 7, 2016 at 6:22

Nitya Kumar

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2 Comments

J. Chomel Over a year ago

While this code snippet may solve the question, including an explanation really helps to improve the quality of your post. Remember that you are answering the question for readers in the future, and those people might not know the reasons for your code suggestion.

FlameDra Over a year ago

I need to use the reduce method to get the length.

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