If you are actively working on your Function in the Twilio Console, you can display live logs that can aid you in debugging your deployed Functions.

To start, click theEnable live logs button near the bottom-right of the Functions editor. As your Function is invoked, any log statements in your code will be displayed in real time.

Given the following Function code, deployed withPublic Visibility:

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exports.handler= function(context,event,callback) {
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console.log("Invoked with: ", event);
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returncallback(null,"OK");
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};

If you invoke the Function with some arguments, you should see their values displayed in the console as shown below.

curlhttps://your-domain-2242.twil.io/log-demo?key=value

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In this case, Twilio Functions streamed the start, end, and anyconsole output of the Function into the Twilio console.

If you leave your console session by navigating away or closing the browser window, the log messages that your Function(s) generate will still be accessible asLogs via the Serverless API.

For example, suppose the above Function generated logs at different error levels (info, warn, and error). You can use theTwilio CLI to retrieve these logs from the Serverless API:

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twilioapi:serverless:v1:services:environments:logs:list\
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--service-sidZSXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX\
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--environment-sidZEXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

The output may look like this:

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[ERROR][2021-10-27T22:07:54Z]: Invoked with:  { key: 'value' }
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[WARNING][2021-10-27T22:07:54Z]: Invoked with:  { key: 'value' }
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[INFO][2021-10-27T22:07:54Z]: Invoked with:  { key: 'value' }

For a less verbose command, you can also install theServerless Toolkit plugin for the CLI and issue the following command instead:

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twilioserverless:logs\
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--service-sid=ZSXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX \
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--environment=ZEXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

Just as before, the output may look like this:

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[ERROR][2021-10-27T22:07:54Z]: Invoked with:  { key: 'value' }
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[WARNING][2021-10-27T22:07:54Z]: Invoked with:  { key: 'value' }
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[INFO][2021-10-27T22:07:54Z]: Invoked with:  { key: 'value' }

For more information about Logs, other ways to retrieve them, and their limitations, please refer to theLogs API Reference.

If you want to run your Function with a fully-featured debugger attached and have the ability to step through your code, then you will need to leverage theServerless Toolkit.

These setup instructions will allow you to run your Function on your local machine and step through its execution using any Node.js supported debugger, such asVisual Studio Code or theChrome Developer Tools.

If your Function returns an error, it will be reported in theDebugger.