访问自执行匿名函数中的变量

Question

as per my knowledge variables inside Self-Executing Anonymous Function are not accessible from outside but how come var q is accessible outside and why not var p then

(function(){ 
    var p = q = 20;
})()
alert(q) --> 10
alert(p) --> p is undefined is the result im getting,

Answer 1

Variables defined within a anonymous function will not be accessible outside. However in your example you are setting variable p as a scoped variable & q as a global variable. The correct way you are looking for here would be:

var p;
var q;
p = q = 20;

Answer 2

To avoid global variable you need to add var , const or let before each variable name. If you omit these keywords the variable begin global. In your case q is global