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Documentation Index

Fetch the complete documentation index at: https://docs.uselayers.com/llms.txt

Use this file to discover all available pages before exploring further.

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Overview

Functions let you create computed attributes with JavaScript. Use a Function when you need a value that is not already stored on the product, such as discount percentage, SKU coverage, average margin, or a custom label based on several product fields. A Function has three parts:
  • Input query - The product data the Function can read.
  • JS function - The JavaScript that calculates the value.
  • Output schema - The type and shape of the value the Function returns.
Functions run during catalog processing. After a Function is saved and compiled, Layers recalculates products in the background and stores the returned value as a computed attribute.
The JS function editor is currently in beta. Existing derived attributes and JSONLogic-based computed attributes continue to work.

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Prerequisites

Before you create a Function, make sure:
  • Your products have completed a catalog sync.
  • The product data you want to use exists in Layers, such as variants, tags, prices, metafields, or collection titles.
  • You know how the result should be used: searchable, filterable, sortable, visible in API responses, or available as a storefront facet.

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Create a Function

1

Open Attributes

Go to Catalog & Data > Attributes, then click Create Attribute.
2

Choose Computed Attribute

Select Computed Attribute. This opens the Function editor.
3

Name the attribute

Enter a clear name, such as “Discount Percentage” or “Inventory Health”. Layers creates a computed attribute code from the name.
4

Choose a template or start from scratch

Click Templates to start from a built-in recipe, or write your own Function in the editor.
5

Define the input query

In Select inputs, select only the product fields your Function needs. Smaller input queries are easier to review and faster to process.
6

Define the output schema

In Define outputs, describe the value your Function returns. The schema tells Layers whether the result is a number, string, boolean, array, or object.
7

Preview with a product

Open Test results, choose a product, and click Run. Review Received data and Returned data before saving.
8

Save the attribute

Save the attribute. Layers compiles the Function and recalculates product values in the background.

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Input query

The input query controls what product data your Function receives. You can use fields such as:
  • title, vendor, productType, handle
  • available, publishedAt, createdAt, updatedAt
  • tags, namedTags, collectionTitles
  • priceRange
  • variants
  • metafields
  • category, options, images, featuredMedia
For variant data, select the variant fields you need, such as price, compareAtPrice, cost, sku, available, inventoryQuantity, or createdAt.
Use Received data in Test results to confirm the exact data shape before you save.

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Output schema

The output schema tells Layers what your Function returns. Supported output types are:
  • number
  • string
  • boolean
  • array
  • object
For a single returned value, use one output field. Layers stores the value directly on the computed attribute. For multiple returned values, define multiple output fields. Layers stores the parent result as an object and creates generated sub-fields for each output field. You can configure each sub-field for filtering, sorting, and faceting separately.
If a Function returns null, or returns an empty value for a product, Layers excludes that computed value from the product. This keeps empty computed attributes out of API responses and facet results.

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Preview and compile status

The editor shows a compile status:
  • Not compiled - The Function has not been compiled yet.
  • Queued - The Function is waiting to compile.
  • Compiling - Layers is compiling the Function.
  • Ready - The Function compiled successfully and can run during catalog processing.
  • Failed - Layers could not compile the Function. Review the compile error in the editor.
Use Test results before saving. The preview shows:
  • Console output - Logs captured while the Function ran.
  • Received data - The input assembled from your input query.
  • Returned data - The value returned by the Function.

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Function limits

Functions are designed for product data transformation. They must be synchronous and self-contained. Supported:
  • Plain JavaScript helper functions.
  • Array methods such as map, filter, and reduce.
  • Built-in JavaScript methods for strings, numbers, objects, arrays, dates, Math, and JSON.
Not supported:
  • Imports or require.
  • Network calls such as fetch.
  • Async functions, await, and Promise APIs.
  • Timers such as setTimeout or setInterval.
  • Classes.
  • for, for...of, for...in, while, and do...while loops.
  • Recursive functions.

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Troubleshooting

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The Run button is disabled

Select a product in the Preview panel and make sure the editor does not show a blocking syntax error.

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The Function returns no value

Check Received data to confirm your input query includes the field you expect. If the input is empty, add the missing field to the input query.

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A returned field is missing

Compare Returned data with your output schema. Required fields must be returned for every product where the Function produces a result.

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The output type is rejected

Make sure the returned value matches the output schema. For example, a boolean field must return true or false, not "true" or "false".

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The Function compiles but products do not show values yet

Product recalculation runs in the background after you save. Check again after processing finishes, and confirm the attribute is configured for the place you expect to use it, such as API visibility, filtering, sorting, or storefront facets.

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Next steps