Javascript - if duplicate vowels in word return false, else true

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Javascript

How do I loop through an Array while referencing the Index to see if the array has multiple of the same vowel?


Why on Earth does it return true for ['d','o','g'] and the wrong answer for just aboout everything else?

function hasThreeVowels(str){
    vowels = "aeiou";
    newArray = []
    for( let i = 0; i < str.length; i++){
        if(vowels.includes(str[i])){
            newArray.push(str[i]);
        }
        
    }
    for( let i = 0; i < newArray.length; i++){
        if(newArray[i] === newArray[i+1]){
            return false;
        }
    }
    return true;
}

What I have tried:

    for( let i = 0; i < newArray.length; i++){
        if(newArray[i] === newArray[i+1]){
            return false;
        }
    }
    return true;
}