Slicing the array from the front

In this example, we are adding new items in the language field and then use $slice modifier to trim the array to the first five items. 

MongoDB provides different types of array update operators to update the values of the array fields in the documents and $slice modifier is one of them. This modifier is used to limit the number of array items during a $push operation. Syntax: 

{
  $push: {
     <field>: {
       $each: [ <value1>, <value2>, ... ],
       $slice: <number>
     }
  }
}

• If the value of number is zero, then this modifier will update the array field to an empty array.
• If the value of number is negative, then this modifier will update the array field to contain only the last number items.
• If the value of number is positive, then this modifier will update the array field to contain only the first number items.
• $slice modifier must appear with $each modifier in the $push operator. You are allowed to pass an empty array in the $each modifier which help $slice modifier to show its effect. If you use the $slice modifier without $each modifier, then you will get an error.
• The order in which the modifiers appear in $push operation is immaterial.

In the following examples, we are working with:

Database: w3wiki Collection: contributor Document: two documents that contain the details of the contributor in the form of field-value pairs.