JavaScript数组some()函数的语法、用法与实战示例

arr.some(callback(element[, index[, array]])[, thisArg])

const arr = [1, 3, 5, 8, 9];
const hasEven = arr.some(num => {
  console.log(num); // 输出：1, 3, 5, 8（找到 8 后停止）
  return num % 2 === 0;
});
console.log(hasEven); // true

[].some(() => true); // false

const numbers = [1, 3, 5, 7, 8];
const hasEven = numbers.some(num => num % 2 === 0);
console.log(hasEven); // true

const users = [
  { id: 1, name: "Alice", isLoggedIn: true },
  { id: 2, name: "Bob", isLoggedIn: false },
  { id: 3, name: "Charlie", isLoggedIn: true },
];

const hasLoggedOut = users.some(user => !user.isLoggedIn);
console.log(hasLoggedOut); // true

const whiteList = ["/login", "/register", "/public"];

const isAllowed = (path) => {
  return whiteList.some(pattern => path.startsWith(pattern));
};

console.log(isAllowed("/login")); // true
console.log(isAllowed("/admin")); // false

const formFields = [
  { name: "username", value: "", error: "用户名不能为空" },
  { name: "password", value: "123", error: "" },
  { name: "email", value: "test@", error: "邮箱格式错误" },
];

const hasError = formFields.some(field => field.error !== "");
console.log(hasError); // true

// ❌ 错误示例：在回调中修改外部变量
let count = 0;
const arr = [1, 2, 3];
arr.some(num => {
  count++; // 副作用！
  return num > 2;
});

const arr = [1, , 3];
arr.some(num => num === undefined); // false（空位不触发回调）

const bigArray = new Array(1000000).fill(0);
bigArray[999999] = 1;

// ✅ 快速找到非零元素
const hasNonZero = bigArray.some(num => num !== 0); // 仅遍历到最后一个元素