May 3, 2000 - Detecting Object-Property Relationship
May 3, 2000|
Detecting Object-Property Relationship
Tips: May 2000
Yehuda Shiran, Ph.D.
inoperator checks if a given property is defined for a given object. Suppose the object line is of type
line = new Array("aaa", "bbb", "ccc", "ddd", "eee");
We know that the object
line inherited the
Array's properties such as its
length. If we check whether
length is in
length in line), we should get a true value. Notice that the array should not be empty, or else the returned answer will be a false value.
Similarly, the method
hasOwnProperty does exactly what the
in operator does. The expression:
should return a true value.
propertyIsEnumerable() checks, again, that a given property belongs to a given object. Once it belongs, it is automatically enumerable in
for...in loops. The
for...in loop loops through the existing properties of a given object. The check
line.propertyIsEnumerable(length) should return a true value.