Variable scope in JavaScript

1<script type= "text/javascript" >2         varA = 10;3        4         varBar = (function () {5Console.log (a);//undefine6             varA = 20;7             return function() {a + = 1; Console.log (a);};8         })();9 Bar ();Ten Bar (); one</script>

• Looking at the code above, when the global variable A is declared, A is typed in the function expression, and a variable with the same name is declared, we can see that the result is:

• Description When a global variable is declared again in a function expression, a defaults to a value of Undefined.
• Here we delete the variable declarations in the function expression to see the result:

therefore, function expressions, variable declarations their default values are Undefined.

Variable scope in JavaScript