How do i get an element from an array in mongodb?

The following example queries for all documents where the field tags value is an array with exactly two elements, "red" and "blank", in the specified order:

If, instead, you wish to find an array that contains both the elements "red" and "blank", without regard to order or other elements in the array, use the $all operator:

The following example queries for all documents where tags is an array that contains the string "red" as one of its elements:

For example, the following operation queries for all documents where the array dim_cm contains at least one element whose value is greater than 25.

When specifying compound conditions on array elements, you can specify the query such that either a single array element meets these condition or any combination of array elements meets the conditions.

For additional query examples, see:

• Query Documents

• Query on Embedded/Nested Documents

• Query an Array of Embedded Documents

Returns the element at the specified array index.

$arrayElemAt has the following syntax:

{ $arrayElemAt: [ ,  ] }

The expression can be any valid expression that resolves to an array.

The expression can be any valid expression that resolves to an integer:

• If the expression resolves to zero or a positive integer, $arrayElemAt returns the element at the idx position, counting from the start of the array.

• If the expression resolves to a negative integer, $arrayElemAt returns the element at the idx position, counting from the end of the array.

If idx exceeds the array bounds, $arrayElemAt does not return a result.

For more information on expressions, see Expressions.

For more information on expressions, see Expressions.

A collection named users contains the following documents:

{ "_id" : 1, "name" : "dave123", favorites: [ "chocolate", "cake", "butter", "apples" ] }
{ "_id" : 2, "name" : "li", favorites: [ "apples", "pudding", "pie" ] }
{ "_id" : 3, "name" : "ahn", favorites: [ "pears", "pecans", "chocolate", "cherries" ] }
{ "_id" : 4, "name" : "ty", favorites: [ "ice cream" ] }

The following example returns the first and last element in the favorites array:

db.users.aggregate([
   {
     $project:
      {
         name: 1,
         first: { $arrayElemAt: [ "$favorites", 0 ] },
         last: { $arrayElemAt: [ "$favorites", -1 ] }
      }
   }
])

The operation returns the following results:

{ "_id" : 1, "name" : "dave123", "first" : "chocolate", "last" : "apples" }
{ "_id" : 2, "name" : "li", "first" : "apples", "last" : "pie" }
{ "_id" : 3, "name" : "ahn", "first" : "pears", "last" : "cherries" }
{ "_id" : 4, "name" : "ty", "first" : "ice cream", "last" : "ice cream" }

• $first

• $last

• $slice

• Array Expression Operators