(c) Variables and constants

• Constant

The constant types in JS mainly include string constants, numeric constants, Boolean constants, null and undefined, and so on.

• Variable

The name of the JS variable must begin with a letter or underscore. You can follow an underscore or a number, but you cannot use a special symbol.

The scope of the JS variable has global and local points, and when the variable has the same name, local scope takes precedence over the global scope.

• Deepen the understanding of data types

(c) Variables and constants