Array Update Operators

Rahul's skills is an array. Do not $set the whole array unless you intend to replace it. These operators change membership. Matching a specific element by position ($, $[]) is a later lesson — here we add and remove.

db.users.updateOne(
  { email: "rahul@example.com" },
  { $push: { skills: "Express" } }
)

{ skills: ["Node.js", "MongoDB", "Express"] }

db.users.updateOne(
  { email: "rahul@example.com" },
  { $addToSet: { skills: "MongoDB" } }
)
// skills unchanged — MongoDB was already present

db.users.updateOne(
  { email: "rahul@example.com" },
  { $pull: { skills: "Express" } }
)

db.users.updateOne(
  { email: "rahul@example.com" },
  { $pullAll: { skills: ["Express", "GraphQL"] } }
)

db.users.updateOne(
  { email: "rahul@example.com" },
  { $pop: { skills: 1 } }   // 1 = last element, -1 = first
)

• `$push` — append. Use $each to append several: { $push: { skills: { $each: ["Redis", "SQL"] } } }.
• `$addToSet` — set semantics for that value. Nested objects must match exactly to count as duplicates.
• `$pull` — remove every equal value (or a condition). `$pullAll` — remove every value in a list.
• `$pop` — 1 last, -1 first. Not 'pop index 3'.