SOURCE

function findMostWord(article) {
    // 判断合法性
    if (!article) return;
    // 参数处理
    article = article.trim().toLowerCase();
    let wordList = article.match(/[a-z]+/g),
        visited = [],
        maxNum = 0,
        maxWord = "";
    console.log(wordList)
    article = " " + wordList.join("  ") + " ";
    // 遍历判断单词出现次数
    wordList.forEach(function (item) {
        if (visited.indexOf(item) < 0) {
            let word = new RegExp(" " + item + " ", "g"),
                num = article.match(word).length;
            if (num > maxNum) {
                maxNum = num;
                maxWord = item;
            }
        }
    });
    return maxWord + "  " + maxNum;
}

console.log(findMostWord("I am sam say yes yes yes"))