Неопределенный индекс массива JavaScript

function longestWords(str){
    let words = str.split(" ");
    let size = 0;
    let max = [''];

    for(let i=0; i<words.length; i++){
        if (words[i].length >= size){
            size = words[i].length;
            if (max[max.length-1].length <words[i].length){
                max = [];
                max.push(words[i]);
            }
            else{
                max = [...max,words[i]];
            }
        }
    }
    return [...max];
}

console.info(longestWords("I woke up early today"));
console.info(longestWords("I went straight to the beach"));