闭包，传入函数，匿名函数 in javascript

gistfile1.js

//inspired by http://www.liaoxuefeng.com/wiki/001374738125095c955c1e6d8bb493182103fac9270762a000/001386819873910807d8c322ca74d269c9f80f747330a52000
//python version on the way 

//a javascript clousure sample 
function testSum() {
    var argsArr = Array.prototype.slice.call(arguments);
    function sum() {
        //clousure can get the acess to outer args and private variable
        var sumNum = 0;
        for(var i =0, len = argsArr.length; i < len; i++){
            sumNum += argsArr[i];
        }
        return sumNum;
    }
    return sum;
}

var f = testSum(1, 2, 3);
var x = testSum(1, 2, 3);
console.log(f === x);
f();

//pass a function as a parameter
var numbers = [1, 2, 3, 4, 5];
function square(x) {
    return x * x;
}
numbers.map(square);

//map generically use, not only in array
var map = Array.prototype.map;
map.call(numbers, square);
//use it in string
var str = 'This is cool stuff';
function upperstr(s) {
    return s.charCodeAt(0);
}
map.call(str, upperstr);
//anonymous function = callbackk function = lambda in python
map.call(numbers, function (x) {
    return x + 20;
});