javascript作用域的一个小例子

function outer()
{
var a = 1;

function inner() {
var d = 4;
}

var b = 2;

if (a == 1) {
var c = 3;
}

document.writeln(a);
document.writeln(b);
document.writeln(c);
document.writeln(d);
}

outer();