Intellectually, the null
type is
nearly identical to the undefined
type. Like the
undefined datatype, the
null datatype is used to represent a lack of
data and has only one legal value, the primitive value
null
. The null
value is not
assigned by the interpreter automatically, but rather by us
deliberately.
We assign null
to a variable, array element, or
object property to indicate that the specified data container does
not contain a legal number, string, boolean, array, or object value.
Note that null
only compares equal to itself and
undefined
:
null == undefined; // true null == null; // true
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