如何实现PromiseLike接口？

class CustomPromise {
  constructor(executor) {
    this.state = 'pending';
    this.value = undefined;
    this.onFulfilledCallbacks = [];
    this.onRejectedCallbacks = [];

    const resolve = (value) => {
      if (this.state === 'pending') {
        this.state = 'fulfilled';
        this.value = value;
        this.onFulfilledCallbacks.forEach((callback) => callback(this.value));
      }
    };

    const reject = (reason) => {
      if (this.state === 'pending') {
        this.state = 'rejected';
        this.value = reason;
        this.onRejectedCallbacks.forEach((callback) => callback(this.value));
      }
    };

    try {
      executor(resolve, reject);
    } catch (error) {
      reject(error);
    }
  }

  then(onFulfilled, onRejected) {
    const fulfilledCallback = typeof onFulfilled === 'function' ? onFulfilled : (value) => value;
    const rejectedCallback = typeof onRejected === 'function' ? onRejected : (reason) => { throw reason; };

    return new CustomPromise((resolve, reject) => {
      const handleFulfilled = (value) => {
        try {
          const result = fulfilledCallback(value);
          if (result instanceof CustomPromise) {
            result.then(resolve, reject);
          } else {
            resolve(result);
          }
        } catch (error) {
          reject(error);
        }
      };

      const handleRejected = (reason) => {
        try {
          const result = rejectedCallback(reason);
          if (result instanceof CustomPromise) {
            result.then(resolve, reject);
          } else {
            reject(result);
          }
        } catch (error) {
          reject(error);
        }
      };

      if (this.state === 'fulfilled') {
        setTimeout(() => handleFulfilled(this.value), 0);
      } else if (this.state === 'rejected') {
        setTimeout(() => handleRejected(this.value), 0);
      } else {
        this.onFulfilledCallbacks.push(handleFulfilled);
        this.onRejectedCallbacks.push(handleRejected);
      }
    });
  }

  catch(onRejected) {
    return this.then(undefined, onRejected);
  }

  finally(onFinally) {
    return this.then(
      (value) => CustomPromise.resolve(onFinally()).then(() => value),
      (reason) => CustomPromise.resolve(onFinally()).then(() => { throw reason; })
    );
  }

  static resolve(value) {
    return new CustomPromise((resolve) => resolve(value));
  }

  static reject(reason) {
    return new CustomPromise((_, reject) => reject(reason));
  }

  static all(promises) {
    return new CustomPromise((resolve, reject) => {
      const results = [];
      let completedCount = 0;

      const handleResolve = (index, value) => {
        results[index] = value;
        completedCount++;

        if (completedCount === promises.length) {
          resolve(results);
        }
      };

      const handleReject = (reason) => {
        reject(reason);
      };

      promises.forEach((promise, index) => {
        promise.then((value) => handleResolve(index, value), handleReject);
      });
    });
  }

  static race(promises) {
    return new CustomPromise((resolve, reject) => {
      promises.forEach((promise) => {
        promise.then(resolve, reject);
      });
    });
  }
}