Global variables and local variables in JS

Since JS uses only two scopes, it corresponds to both types of variables.

1: Global variables--global scope is accessible.

2: Local variable--can only be accessed at the current scope.

In JS, there is a special case, the variable declared within the scope of the function, not with the Var word, then the variable is a global variable.

Let's look at an example:

Summarize:

1: Within a subset scope is a variable that can access the parent scope (or the previous level), but the parent scope is a variable that cannot be accessed into a subset scope.

2: Variables that are not declared with VAR are global variables and are not recommended for use.

3: Variables are destroyed after they are out of scope, global variables are destroyed when the page is closed or the browser is closed, so use global variables as little as possible, which takes up memory space.

Global variables and local variables in JS