CODEWITHSUNDEEP
javascript
Keith Grout
Keith Grout

Reputation: 909

Why is Javascript 'every' function returning false?

I have a quick question on why my function is returning false, when I expect it to be returning true. I have looked at the documentation for Array.prototype.every, and I still can't seem to find it. Thanks for your help in advance.

For some context, this is part of a coderbyte question called arithGeo. The current function I am working on here is supposed to return true if the difference between each element is the same. Here, I expect this to return true, since each element is 5 apart from the next.

Here is my function 

var arr = [5, 10, 15];
function isArith(arr){
    var diff = arr[1] - arr[0];
    return arr.every(function(val, ind, col){
      // if statement checks to make sure I stay in bounds.
      if(col[ind + 1] !== undefined){
         var next = col[ind + 1] - val;
         console.log(diff === next   );
         // logging shows the following statement to be true, for every iteration
         return diff === next; 
      }
    });
}


var arith = isArith(arr);
console.log('arith: ', arith) // logs false

Upvotes: 0

Views: 1205

Answers (2)

Amadan
Amadan

Reputation: 198334

When you reach the last element, you test to see if there is a next element so you don't compare the last element with nothing. That's great. But in that case, you forget to return anything, and the default return is undefined, which is falsy. Just put in else return true.

Upvotes: 2

Pointy
Pointy

Reputation: 413737

On the last iteration you'll return undefined, which will be interpreted as false. The code does that because if the if fails (which it does on the last element) there's no return statement. If you add return true to the end after the if it should work.

Upvotes: 3

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