var arr = [1, 2, 3];
function f(a) {
    a[0] = null;
}
f(arr);                         // null 2 3
for (var i = 0; i < 3; i++) {
    document.write(arr[i]);
}

var arr = [1, 2, 3];
function f(a) {
    a = null;
}
f(arr);                         // 1 2 3
for (var i = 0; i < 3; i++) {
    document.write(arr[i]);
}

var a = 3;
function f(b) {
    b = 4;
}
f(a);
document.write(a);          // 3

(funtion () {
    var msg = "xxx";
    wnidow.onunload = function () {
            ...do something...
    }
})

this.f = function () {
    if (arguments.length == 1) {
        this.f1(arguments[0]);
    } else if (arguments.length == 2) {
        this.f1(arguments[0], arguments[1]);
    }
}
this.f1 = function (a) {
        ....
}
this.f2 = function (a, b) {
        ....
}

alert((function (n) {
    if (n <= 1) {
        return 1;
    } else {
        return n + arguments.callee(n-1);
    }
})(100));

function power(base, exponent) {
    var result = 1;
    if (exponent == undefined) {
        exponent = 2;
    }
    for (var i = 1; i <= exponent; i++) {
        result *= base;
    }
    return result;
}

(function(a) {alert (a); })(‘abc‘)