Use JavaScript code in Zaps

Code steps allow Zaps to run small snippets of Python or JavaScript. This tutorial is for JavaScript code steps, but you can also learn how to use Python code in your Zaps.

Code steps can be used as both triggers and actions.

Note

JavaScript is an advanced programming language.

• If you're not familiar with JavaScript, you should ask a developer for help.
• Plans with Premier Support have access to basic support for Code by Zapier steps. Premier Support won't write or debug your code, but can assist with how Code by Zapier processes code.
• For plans without Premier Support or for additional help beyond Premier Support, visit the Zapier Community's Code resources.

Tip

You can generate code steps using AI.

The JavaScript environment

The environment running is Node.js 18. Your script is sandboxed and can only run for a limited amount of time and within a limited amount of memory—the exact limits depend on the plan you are using.

Note

• AWS does not prevent deprecated Node run times from running.
• Dates and times in Code actions use the UTC timezone, even if a different one is set for the account or the Zap.

Input data for Code steps

You can access data from previous steps via the inputData dictionary variable in your code step. The amount of data that may feed into your script may be large or dynamic. To address this, you must define an inputData mapping by providing a key and value in Zapier's GUI.

You can't map fields from previous Zap steps to the Code field. You must use the Input Data dictionary.

You can create a key/value pair in the Input Data field for each mapped field you want to use in your code.

In Javascript, you can access the inputData dictionary variable values by using the inputData.keyName or inputData["keyName"] notation. Key names are case-sensitive and must be an exact match when referenced.

In the example below, the key name is "defineName" and the value is supplied by the Name field that's mapped from a previous step. In this example, the value supplied by the mapped Name field is "Jane".

Note

It's not possible to map inputData in Code by Zapier triggers.

Output data from Code steps

Code steps return a single output variable, which is an object or array of objects that will be the result of this step. You can explicitly return early.

If the output is an array of objects, subsequent steps will run multiple times, once for each object in the array.

[
    {
        "product_id": 123,
        "name": "world",
        "price": 5.50
    },
    {
        "product_id": 234,
        "name": "planet",
        "price": 11.00
    }
]

Example

In this example, each object in the array is returned separately. Subsequent actions will run once for each object.

To return the whole array as line items instead, you can add line_items as the parent key for the output.

{
    "first_name": "Zap",
    "last_name": "Zaplar",
    "invoice_id": 123456,
    "total_price": 55.50,
    "line_items" : [
        {
            "product_id": 123,
            "name": "world",
            "price": 5.50
        },
        {
                "product_id": 234,
                "name": "planet",
                "price": 11.00
        }
    ]
};

Example

In this example, the array is returned as a set of line items. Any subsequent actions will only run once.

If you use Code by Zapier as the Zap's trigger and an empty array is returned, nothing will happen. The behavior will be similar to a polling trigger that did not get any results in the HTTP response. This functionality is exclusive to triggers.

Utilities in Code steps

There are a few utilities you have access to in Code steps:

• (Optional) callback(err, output): a callback if you need to do asynchronous work—whatever you set to the output data variable is ignored since it's provided directly here. The Zap will inspect the code and make a best guess as to whether it's using a callback or not.

Note

Invoking callback(err, output) tells Zapier that your task is done executing. If you have multiple asynchronous calls, each invoking callback(err, output) with their desired responses, only the first one to execute will count. Subsequent invocations to callback(err, output) will be picked up by the next execution of your Zap, but will not affect that task's execution, other than side effects like console.log() calls.

• fetch: an easy to use HTTP client.
• console.log: this utility allows you to debug your function. You'll need to test your Zap to see the values. The logs are returned in a runtime_meta added automatically to the output.
• StoreClient : a built-in utility for storing and retrieving data between Zap runs.

Testing and debugging Code steps

Running your Zap via the dashboard is the canonical way to confirm the behavior you expect. Your Zap History will have all relevant details around the Code step's inputData, output and logs. The test step in the editor can be used for a tighter feedback loop.

Limitations with Code steps

• The environment in which your Code steps run (AWS Lambda) has an I/O limit of 6 MB. The total size of the code and the data processed by the Code step cannot exceed that. If you're hitting this error, try to limit the amount of data returned from your function. For instance, don't return an entire JSON structure, just the keys you need.
• You cannot require external libraries, or install or import libraries commonly referred to as "npm modules". Only the standard node.js library and the fetch package are available in the Code by Zapier app. fetch is already included in the namespace.
• There are different Code rate limits and throttling, depending on what Zapier plan you’re on. Your Zap will error if it exceeds these limits.

Troubleshooting errors

Some common error messages you might encounter include:

• Scripting payload too large: this means the total amount of data returned from your function is too large. See Limitations with code steps.
• NoneType object does not support item assignment: this error can happen when you redefine some of the important variables in the function, such as callback. Lambda expects callback to be there to complete an async function, so it'll produce errors if it's redefined.
• Process exited before completing request: this typically happens if your script completes without calling callback. The most common case is if your fetch().then() doesn't have a .catch() for errors. Adding a .catch(callback) will solve this, as the error will be passed as the first argument.
• SyntaxErrors or other bugs: JavaScript is a fairly complex language and syntax errors can happen for a variety of reasons. We recommend using a linter like JSHint to automatically check your code and highlight specific issues.

Note

If you're using a linter, you can safely ignore warnings about unused variables for inputData, output, fetch or callback. Those are provided for your convenience, but you don't need to use them. If you see something else listed, you may need to debug your code.