根据每个单词的第一个字母筛选包含元素的数组

function filterArrayByFirstLetter(arr, letters) {
  var result = [];
  
  for (var i = 0; i < arr.length; i++) {
    var firstLetter = arr[i][0].toLowerCase();
    
    if (letters.includes(firstLetter)) {
      result.push(arr[i]);
    }
  }
  
  return result;
}

// 示例用法
var array = ["apple", "banana", "cat", "dog", "elephant"];
var lettersToFilter = ["a", "b", "c"];

var filteredArray = filterArrayByFirstLetter(array, lettersToFilter);
console.log(filteredArray);