In MongoDB, we use array operators and expressions to work on arrays and perform arithmetic operations and complex data manipulations. Here are some use cases for these operators:
1. `$addToSet` The $addToSet operator adds a value to an array unless the value is already present, in which case $addToSet does nothing to that array.
\`\`\` db.collection.update( { \_id: 1 }, { $addToSet: { letters: { $each: [ “a”, “c” ] } } } ) \`\`\` 1. `$pop` The $pop operator removes the first or last element of an array. Pass $pop a value of -1 to remove the first element of an array and 1 to remove the last element in an array. \`\`\` db.collection.update( { \_id: 1 }, { $pop: { scores: -1 } } ) \`\`\`1. `$push` The $push operator appends a specified value to an array.
\`\`\` db.collection.update( { \_id: 1 }, { $push: { scores: { $each: [ 90, 92, 85 ] } } } ) \`\`\`1. `$pull` The $pull operator removes all instances of a value from an existing array.
\`\`\` db.collection.update( { \_id: 1 }, { $pull: { scores: { $in: [90, 92] } } } ) \`\`\` 1. `$size` The $size operator matches any array with the number of elements specified by the $size operator. \`\`\` db.collection.find( { scores: { $size: 3 } } ) \`\`\` These are just some of the array operators in MongoDB and there are many others that you can find in the MongoDB documentation. The specific operator’s documentation can be referred to for the syntax and argument details.