Scope變量衝突以及 IIEF

function foo() {
    function bar(a) {
        i =8;//這邊聲明衝突
        console.log(a+i);

    }
    for (var i =0 ;i<10; i++){
        bar(i);
    }
}
foo();

IIEF Immediately Invoked Function Expression
(function foo(){ /* code */ })();
As the primary use of IIFE is to introduce function-level scope, naming
the function is not really required.
a slight variation of IIFE：
(function(){ /* code */ }());
也可以傳值進來：

(function foo(b) {
var a = 2;
console.log( a + b );
})(3); //prints 5