delete | NN 4 IE 4 ECMA 1
The delete operator removes a property from an object (e.g., a prototype property from an instance of an object to whose static object your script added the prototype earlier) or an item from a script-generated array. Removing an array entry does not alter the array's length or the numerical indexes of existing items. Instead, the value of the deleted item is simply undefined. The delete operator is not a memory management tool.
Example
    delete myString.author;