Java Reference
In-Depth Information
Null
null
means "no value". It can be thought of as a placeholder that JavaScript uses to say
"there should be an value here, but there isn't at the moment."
undefined
and
null
are both "non-value" values. They are similar, although they behave
slightly differently. For example, if you try to do sums with them:
10 + null // null behaves like zero
<< 10
10 + undefined // undefined is not a number
<< NaN
null
is coerced to be
0
, making the sum possible whereas
undefined
is coerced to
NaN
,
making the sum impossible to perform.
Values tend to be set to
undefined
by JavaScript, whereas values are usually set to
null
manually by the programmer.
