The delete operator deletes a property, array element, or variable of the object specified by the operand. It will return true if the delete operation is successful, if the operand cannot be deleted,
It will return false. Not all properties and variables can be deleted. Some internal core properties and client properties cannot be deleted. Users declared with the var statement
Defined variables cannot be deleted either. If the operand used by delete is a non-existent property, it will return true (ECMAScript standard stipulates that when the delete operation
It returns true when the operand is not a property, array element, or variable).
var o = {x:1, y: 2}; //Define a variable
delete ox; //Delete the x attribute of the o object and return true
typeof ox; //return undefined
delete ox; //return true
delete o; //Cannot delete variables
delete 1; //The integer variable value 1 cannot be deleted
x = 1; //
delete x; //Can be deleted, return true