# Examples

## Example 1: Webhooks

Below is a **Node.js + Express** example of what the code for your webhook endpoint could look like:

```javascript
//Your webhooks payload endpoint
app.post("/your/webhook/payload-url", function(req, res) {
  const body = req.body;
  
  try {
    if (body.event === 'PARTICIPANT_REACHED_A_GOAL') {
      // Write code here to do something when a participant wins a reward
      console.log(`${body.data.participant.email} just won this reward: ${body.data.reward.description}`);

      // If the reward is approved
      if (body.data && body.data.reward && body.data.reward.approved) {
        // Do something
      }
      
      // If this is a double-sided reward, use body.data.reward.isReferrer to determine if this is for the referrer or referred person
      if (body.data && body.data.reward && body.data.reward.isReferrer) {
        // Do something
        
        // Optional: If you set metadata on the CampaignReward object, you can reference it:
        if (body.data.reward.metadata && body.data.reward.metadata["proRewardValue"]) {
            console.log(`${body.data.participant.email} earned an amount of ${body.data.reward.metadata["proRewardValue"]}.`);
        }
      }
      
      // Optional: If this is the referrer that unlocked the reward, you can get the details of the person that they referred
      if (body.data.reward.isReferrer && body.data.participant.referee) {
          console.log(`${body.data.participant.referee.email} was the person referred by ${body.data.participant.email}.`);
      }      

    } else if (body.event === 'NEW_PARTICIPANT_ADDED') {
      // Write code here to do something when a new participant is added    
      console.log(`${body.data.email} just joined via source: ${body.data.referralSource}.`);
            
    } else if (body.event === 'CAMPAIGN_ENDED') {
      // Write code here to do something when a program ends
      console.log(`${body.data.name} just ended with ${body.data.referralCount} total referrals!`);
            
    }
  
  } catch (err) {
    res.status(400).end();
  }
  res.json({received: true});
});
```

{% hint style="info" %}
**Helpful tips:**

* To see the different sample data from webhook request payloads, see [Events](/developer-tools/webhooks/events-reference.md)
* If you reference [reward metadata](https://docs.growsurf.com/developer-tools/webhooks/events-reference#campaign_ended) in your *New Participant Reward* events, your marketing team can update these values anytime in the future from the Program Editor without getting developers involved.
  {% endhint %}

## Example 2: Webhooks (with secret)

Below is a **Node.js + Express** example (using the [crypto-js](https://github.com/brix/crypto-js) library) of what the code for your webhook endpoint could look like:

```javascript
//Your webhooks payload endpoint
app.post("/your/webhook/payload-url", function(req, res) {
  const body = req.body;
  const signature = req.get("GrowSurf-Signature");
  
  try {
    // Validate the signature
    validateSignature(body, signature);
  
    // Do work!.....
    // Write your code in here...  
  
  } catch (err) {
    res.status(400).end();
  }
  res.json({received: true});
});

/**
 * Compares the GrowSurf header provided signature against the expected
 * signature.
 *
 * @param {Object} body the request body provided by GrowSurf
 * @param {String} signature the signature hash value provided within the header of the request
 * @returns {Boolean} valid true if the expected matches the given
 * @throws {Exception} thrown if the expected signature value does not match the given
 */
const validateSignature = function(body, signature) {
  // Extract
  let parts = signature.split(",");
  // t value
  let timestamp = parts[0].split("=")[1];
  // v value
  let hash = parts[1].split("=")[1];
  // Generate hash
  let message = (timestamp + "." + JSON.stringify(body));
  let expected = CryptoJS.HmacSHA256(message, "YOUR-SECRET-TOKEN").toString();

  // Validate/Compare
  if(expected === hash) {
    return true;
  } else {
    throw new Error("Invalid Signature");
  }
}
```


---

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