Why run time error on undefined?

JavaScript
1

I’m trying to understand why this works.

var twoSum = function(nums, target) {
    let result = nums.reduce((answers, value, index, src) =>{
           let pair = src.indexOf(target-value);
           return (answers.length < 2) && (pair != -1) && (pair != index) ? [...answers, index]        :answers;
    },[]);
    return result;
};

But this gives me a runtime error that answers is undefined.

var twoSum = function(nums, target) {
    let result = nums.reduce((answers, value, index, src) =>{
           if(answers.length < 2) {
           let pair = src.indexOf(target-value);
           return  (pair != -1) && (pair != index) ? [...answers, index]   :answers;
    },[]);
      } else {
       return answers;
    }
    return result;
};

It seems like the scope of answers should be the same in both cases but obviously is not.

2

Your else clause is outside of the scope of the callback function for the reduce.

3

Thanks for some reasons I assumed the issue was in the if clause.

4

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