js array查找元素

let arr = [1, 2, 3, 4, 5];
let index = arr.indexOf(3);
console.log(index); // 输出: 2

let arr = [1, 2, 3, 4, 5];
let exists = arr.includes(3);
console.log(exists); // 输出: true

let arr = [1, 2, 3, 4, 5];
let found = arr.find(element => element > 3);
console.log(found); // 输出: 4

let arr = [1, 2, 3, 4, 5];
let foundIndex = arr.findIndex(element => element > 3);
console.log(foundIndex); // 输出: 3

let arr = [1, 2, 3, 4, 5];
let filtered = arr.filter(element => element > 3);
console.log(filtered); // 输出: [4, 5]

function binarySearch(arr, target) {
  let left = 0;
  let right = arr.length - 1;
  
  while (left <= right) {
    let mid = Math.floor((left + right) / 2);
    if (arr[mid] === target) {
      return mid;
    } else if (arr[mid] < target) {
      left = mid + 1;
    } else {
      right = mid - 1;
    }
  }
  return -1;
}

let sortedArr = [1, 2, 3, 4, 5];
let index = binarySearch(sortedArr, 3);
console.log(index); // 输出: 2