[프로그래머스 bfs] 단어 변환 js javascript

function solution(begin, target, words) {

    if (!words.includes(target)) return 0;

  
    let queue = [[begin, 0]]; 
    let wordAll = new Set(words); 
    let now = begin;
    let answer = 0;
 
    function findSimilar(word1, word2) {
        let diff = 0;
        for (let i = 0; i < word1.length; i++) {
            if (word1[i] !== word2[i])
                diff++;
            if (diff > 1) return false; 
        }
        return diff === 1; 
    }

  
    while (queue.length > 0) {
        let [current, step] = queue.shift();

      
        if (current === target) return step;

     
        for (let word of wordAll) {
            if (findSimilar(current, word)) {
                queue.push([word, step + 1]); 
                wordAll.delete(word); // 방문한 단어는 Set에서 제거
            }
        }
    }

  
    return 0;
}

아직도 이해가 잘 안 된다.........................