如何检查数组中是否已存在元素

function checkElement(array, target) {
  for (let i = 0; i < array.length; i++) {
    if (array[i] === target) {
      return true;
    }
  }
  return false;
}

const array = [1, 2, 3, 4, 5];
const target = 3;

console.log(checkElement(array, target)); // 输出：true

function checkElement(array, target) {
  const set = new Set(array);
  return set.has(target);
}

const array = [1, 2, 3, 4, 5];
const target = 3;

console.log(checkElement(array, target)); // 输出：true

function checkElement(array, target) {
  return array.indexOf(target) >= 0;
}

const array = [1, 2, 3, 4, 5];
const target = 3;

console.log(checkElement(array, target)); // 输出：true

function checkElement(array, target) {
  return array.includes(target);
}

const array = [1, 2, 3, 4, 5];
const target = 3;

console.log(checkElement(array, target)); // 输出：true