# bson_append_undefined()

## Synopsis

    bool
    bson_append_undefined (bson_t     *bson,
                           const char *key,
                           int         key_length);

## Parameters

bson | A bson_t.
key | An ASCII C string containing the name of the field.
key_length | The length of key in bytes, or -1 to determine the length with strlen().

## Description

The bson_append_undefined() function shall append a new element to bson of type BSON_TYPE_UNDEFINED. Undefined is common in Javascript. However, this element type is deprecated and should not be used in new code.

## Returns

true if the operation was applied successfully, otherwise false and bson should be discarded.