1.void operates the expression and ignores its return value, such as void (1 2), void (0)
2.typeof returns the type of variable or value, such as typeof(void 1 2) ,typeof(void(1 2))
Due to operator precedence, the operation process of void 1 2 is:
3.new is used to create an object instance column of the specified class
4.delete deletes the instance column attribute. There are several points that must be paid attention to when deleting:
1. Only the actual column attributes will be deleted, but the object will not be deleted