javaScript中匿名函数的传参及赋值

var a = (function (){
    var i = 1
    i++;
    return i;
})(a);
console.log(a);//a=2;


var b=5;
var a = (function(){
    var i = 1;
    return b+i;
})(b);
console.log(a);//a=6


var a = (function(){
    var i=1;
    return i;
})();
console.log(a);//a=1


var a = (function(){
    var i=1;
})();
console.log(a);//a=undefind