Which operator would you use to add a value to the end of an array in a document?

The operator used to add a value to the end of an array in a document is the $push operator. This operator is specifically designed for this purpose, allowing you to append a new element to an existing array field within a MongoDB document.

When you utilize $push in an update operation, MongoDB will modify the document by adding the specified value to the end of the targeted array. This is particularly useful when you need to maintain a list or collection of items, ensuring that new entries are accumulated in the sequence they are added.

Options like $add, $insert, and $append do not serve the function of appending elements to an array in a document. The $add operator, for instance, is related to arithmetic operations and is not applicable to arrays, while $insert is a method used for inserting documents rather than modifying an existing document's fields. Additionally, $append is not a recognized operator in MongoDB for manipulating array elements. Thus, $push is the precise and correct choice for adding values to an array in MongoDB.