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js实现poll函数

2026-04-07 12:45:36JavaScript

js实现poll函数

实现 Poll 函数的方法

Poll 函数通常用于轮询某个条件或状态，直到满足特定条件或超时。以下是几种实现方式：

基本实现

function poll(fn, condition, interval = 1000, timeout = 30000) {
  const endTime = Date.now() + timeout;

  const checkCondition = (resolve, reject) => {
    Promise.resolve(fn())
      .then(result => {
        if (condition(result)) {
          resolve(result);
        } else if (Date.now() < endTime) {
          setTimeout(checkCondition, interval, resolve, reject);
        } else {
          reject(new Error('Polling timeout'));
        }
      })
      .catch(reject);
  };

  return new Promise(checkCondition);
}

使用 async/await 的实现

async function poll(fn, condition, interval = 1000, timeout = 30000) {
  const endTime = Date.now() + timeout;

  while (Date.now() < endTime) {
    const result = await fn();
    if (condition(result)) return result;
    await new Promise(resolve => setTimeout(resolve, interval));
  }

  throw new Error('Polling timeout');
}

带取消功能的实现

function cancellablePoll(fn, condition, interval = 1000, timeout = 30000) {
  let timer;
  let cancelled = false;

  const promise = new Promise((resolve, reject) => {
    const endTime = Date.now() + timeout;

    const checkCondition = () => {
      if (cancelled) {
        reject(new Error('Polling cancelled'));
        return;
      }

      Promise.resolve(fn())
        .then(result => {
          if (condition(result)) {
            resolve(result);
          } else if (Date.now() < endTime) {
            timer = setTimeout(checkCondition, interval);
          } else {
            reject(new Error('Polling timeout'));
          }
        })
        .catch(reject);
    };

    checkCondition();
  });

  promise.cancel = () => {
    cancelled = true;
    clearTimeout(timer);
  };

  return promise;
}

使用示例

// 示例：轮询直到某个元素出现在DOM中
poll(
  () => document.querySelector('.target-element'),
  element => element !== null,
  500,
  5000
)
  .then(element => console.log('Element found:', element))
  .catch(err => console.error('Polling failed:', err));