Mapping Configuration Recipes

Prerequisites

Read understanding-mapping first for core concepts.

Quick Reference

I want to...	Use this pattern
Rename event	{ name: 'new_name' }
Extract nested value	'data.nested.value'
Set static value	{ value: 'USD' }
Transform value	{ fn: (e) => transform(e) }
Build object	{ map: { key: 'source' } }
Process array	{ loop: ['source', { map: {...} }] }
Gate by consent	{ key: 'data.email', consent: { marketing: true } }
First defined value (fallback)	[{ key: 'data.sku' }, { key: 'data.id' }]
Add a field to a default rule	{ extend: { data: { map: { x: 'path' } } } }
Drop a field from output	{ remove: ['field.path'] }

Common Recipes

GA4 / gtag

Product view → view_item:

product: {
  view: {
    name: 'view_item',
    data: {
      map: {
        currency: { value: 'USD' },
        value: 'data.price',
        items: {
          loop: [
            'nested',
            {
              map: {
                item_id: 'data.id',
                item_name: 'data.name',
                item_category: 'data.category',
                price: 'data.price',
                quantity: { value: 1 },
              },
            },
          ],
        },
      },
    },
  },
}

Order complete → purchase:

order: {
  complete: {
    name: 'purchase',
    data: {
      map: {
        transaction_id: 'data.orderId',
        value: 'data.total',
        currency: 'data.currency',
        items: {
          loop: [
            'nested',
            {
              map: {
                item_id: 'data.id',
                item_name: 'data.name',
                price: 'data.price',
                quantity: 'data.quantity',
              },
            },
          ],
        },
      },
    },
  },
}

Meta Pixel

Product view → ViewContent:

product: {
  view: {
    name: 'ViewContent',
    data: {
      map: {
        content_ids: { fn: (e) => [e.data.id] },
        content_type: { value: 'product' },
        content_name: 'data.name',
        value: 'data.price',
        currency: { value: 'USD' },
      },
    },
  },
}

Order complete → Purchase:

order: {
  complete: {
    name: 'Purchase',
    data: {
      map: {
        content_ids: { fn: (e) => e.nested?.map((n) => n.data.id) ?? [] },
        content_type: { value: 'product' },
        value: 'data.total',
        currency: 'data.currency',
        num_items: { fn: (e) => e.nested?.length ?? 0 },
      },
    },
  },
}

Custom API Destination

Transform to REST API format:

'*': {
  '*': {
    name: { fn: (e) => `${e.entity}_${e.action}` }, // page_view
    data: {
      map: {
        eventName: 'name',
        eventData: 'data',
        userId: 'user.id',
        sessionId: 'user.session',
        timestamp: 'timestamp',
        metadata: {
          map: {
            consent: 'consent',
            globals: 'globals',
          },
        },
      },
    },
  },
}

Conditional Mapping

Different mapping based on event data:

order: {
  complete: [
    // High-value orders get extra tracking
    {
      condition: (e) => (e.data?.total ?? 0) > 500,
      name: 'high_value_purchase',
      data: {
        map: {
          value: 'data.total',
          priority: { value: 'high' },
          notify: { value: true },
        },
      },
    },
    // Standard orders
    {
      name: 'purchase',
      data: { map: { value: 'data.total' } },
    },
  ],
}

Patching Package-Shipped Rules (extend / remove)

Some packages (such as @walkeros/transformer-ga4) ship default mapping rules. Normally a user rule at the same key replaces the default in full. Use extend or remove to patch instead.

Two layers, two keywords:

• extend runs at init (config layer): deep-merges a partial rule onto the shipped default. A null value clears an inherited field.
• remove runs after evaluation (output layer): strips dotted paths from the final data payload. Applied last, always wins.

A rule with neither keyword keeps the existing replace behavior.

{
  "purchase": {
    "extend": {
      "data": { "map": { "affiliation": "params.ep.affiliation" } }
    },
    "remove": ["currency"]
  }
}

This keeps all fields the package ships for purchase, adds affiliation, and strips currency from the output.

For the full reference and the two-layer model, see Mapping.Rule docs.

Value[] Fallback Chains

At any value position, an array of values is a fallback chain: the first entry that resolves to a defined value wins.

{
  "item_id": [
    { "key": "data.sku" },
    { "key": "data.id" },
    { "value": "unknown" }
  ]
}

Use this to try multiple source fields before falling back to a constant.

Consent-Gated Fields

Only include PII if consent granted:

user: {
  login: {
    name: 'login',
    data: {
      map: {
        method: 'data.method',
        // Only include email if marketing consent
        email: {
          key: 'user.email',
          consent: { marketing: true },
        },
        // Only include user ID if functional consent
        userId: {
          key: 'user.id',
          consent: { functional: true },
        },
      },
    },
  },
}

Wildcard Patterns

Catch-all for unmatched events:

// Any product action
product: {
  '*': {
    name: { fn: (e) => `product_${e.action}` },
    data: 'data',
  },
}

// Any click on any entity
'*': {
  click: {
    name: 'element_click',
    data: {
      map: {
        element_type: 'entity',
        element_id: 'data.id',
      },
    },
  },
}

Source-Side Mapping

Transform HTTP input to walkerOS event:

// In source config
{
  mapping: {
    // Map incoming field names to walkerOS structure
    name: { fn: (input) => `${input.entity} ${input.action}` },
    data: 'payload',
    user: {
      map: {
        id: 'userId',
        session: 'sessionId',
      },
    },
  },
}

Debugging Tips

1. Event not mapping? Check entity/action match exactly (case-sensitive)
2. Data missing? Verify source path exists: 'data.nested.field'
3. Function errors? Add null checks: e.data?.price ?? 0
4. Array empty? Confirm nested array exists and has items

Related Skills

• walkeros-understanding-mapping - Core mapping concepts

Reference:

• packages/core/src/mapping.ts - Implementation
• apps/quickstart/src/ - Validated examples