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Use this API to listen for unhandled Promise rejections. The callback triggers when a Promise without a rejection handler is rejected.

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Parameters

PropertyTypeRequiredDescription
callbackFunctionYesHandler executed when an unhandled rejection occurs

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Callback Parameters

PropertyTypeDescription
reasonStringThe rejection reason (typically an error object)
promisePromiseThe rejected Promise instance

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Code Example

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Basic Usage

App({
  onShow() {
    my.onUnhandledRejection((res) => {
      console.log('Unhandled rejection reason:', res.reason);
      console.log('Rejected promise:', res.promise);
    });
  }
});

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Error Logging

App({
  onLaunch() {
    my.onUnhandledRejection((res) => {
      // Log unhandled rejections
      this.logRejection({
        reason: res.reason,
        timestamp: Date.now()
      });
    });
  },

  logRejection(data) {
    my.request({
      url: 'https://api.example.com/errors/rejections',
      method: 'POST',
      data: data
    });
  }
});

​
Development Debugging

App({
  onLaunch() {
    my.getRunScene({
      success: ({ envVersion }) => {
        if (envVersion === 'develop') {
          my.onUnhandledRejection((res) => {
            // Show detailed info in development
            my.alert({
              title: 'Unhandled Promise Rejection',
              content: String(res.reason)
            });
          });
        }
      }
    });
  }
});

​
Common Causes

Unhandled Promise rejections typically occur when: 
// This will trigger onUnhandledRejection
my.request({
  url: 'https://api.example.com/data'
}).then((res) => {
  console.log(res);
});
// Missing .catch()

// Correct approach
my.request({
  url: 'https://api.example.com/data'
}).then((res) => {
  console.log(res);
}).catch((err) => {
  console.error('Request failed:', err);
});

// This will trigger onUnhandledRejection
async function fetchData() {
  const res = await my.request({ url: '...' });
  return res.data;
}

// Correct approach
async function fetchData() {
  try {
    const res = await my.request({ url: '...' });
    return res.data;
  } catch (err) {
    console.error('Failed:', err);
    return null;
  }
}

// Error in .then() without .catch()
fetchData()
  .then((data) => {
    throw new Error('Processing failed');
  });

// Correct approach
fetchData()
  .then((data) => {
    throw new Error('Processing failed');
  })
  .catch((err) => {
    console.error('Chain error:', err);
  });
Always add .catch() handlers to your Promises or use try/catch with async/await to prevent unhandled rejections.

my.offUnhandledRejection

Stop listening for unhandled rejections

my.onError

Listen for JS errors