Unset field in array items using Sanity client patch operation

I understand your challenge! You're trying to unset or clear the projects field within each item of your contentArray. The tricky part is that Sanity's patch operations don't support wildcard paths like contentArray[*].projects directly.

Here are your best options:

Option 1: Patch with specific array item keys (Recommended)

The most reliable approach is to use the _key values to target each array item specifically:

sanityClient
  .patch('9c780fd3-0e54-40ad-80c8-fd27dc19359f')
  .unset([
    'contentArray[_key=="3cd487d4bd8c"].projects',
    'contentArray[_key=="0d5871d6ce7b"].projects'
  ])
  .commit()

If you need to do this dynamically, fetch the document first and build the paths:

const doc = await sanityClient.getDocument('9c780fd3-0e54-40ad-80c8-fd27dc19359f')

const pathsToUnset = doc.contentArray
  .filter(item => item.projects && item.projects.length > 0)
  .map(item => `contentArray[_key=="${item._key}"].projects`)

if (pathsToUnset.length > 0) {
  await sanityClient
    .patch(doc._id)
    .unset(pathsToUnset)
    .commit()
}

Option 2: Replace the entire array

If you want to set all projects to empty arrays (rather than removing the field entirely), you can fetch the document, modify it in JavaScript, and set the entire contentArray:

const doc = await sanityClient.getDocument('9c780fd3-0e54-40ad-80c8-fd27dc19359f')

const updatedContentArray = doc.contentArray.map(item => ({
  ...item,
  projects: []
}))

await sanityClient
  .patch(doc._id)
  .set({ contentArray: updatedContentArray })
  .commit()

Why your attempts didn't work

Your loop approach was close, but each iteration created a separate patch transaction. The syntax contentArray[${index}].projects uses numeric indices, which aren't reliable in Sanity because array items can be reordered. Sanity's patch operations work better with _key references for array items.

The unset(['contentArray.projects']) approach treats the entire array as having a single projects property, which isn't how nested array items work.

unset() vs set() to empty array

• unset(): Completely removes the field from the document
• set({ projects: [] }): Keeps the field but makes it an empty array

Choose based on your schema and whether you want the field to exist or not. If your schema expects the field to always be present, use set() with an empty array.

The key takeaway is to use _key references when targeting specific items within arrays. This gives you precise control over nested fields in array items without having to replace the entire array structure.