var obj = "{a:1,b:2}";  // 看起来像对象的字符串
eval("("+ obj +")")   // {a: 1, b: 2}

var number = 4
(number & number -1) === 0 // true

var a = 4,b = 3
a = a ^ b //  7
b = a ^ b //  4
a = b ^ a //  3

var temp = new Date();
var regex = /\//g;
(temp.toLocaleDateString() + ' ' + temp.toLocaleTimeString().slice(2)).replace(regex,'-');

// "2015-5-7 9:04:10"

new Date("2015-5-7 9:04:10");

// Thu May 07 2015 09:04:10 GMT+0800 (CST)

(new Date).valueOf();

// 1431004132641

var number = "23" 
typeof number // string
typeof +number // number

new Date // Tue May 12 2015 22:21:33 GMT+0800 (CST)
+new Date // 1431440459887

var url = encodeURIComponent('http://segmentfault.com/questions/newest')

// "http%3A%2F%2Fsegmentfault.com%2Fquestions%2Fnewest"

decodeURIComponent(url)
// "http://segmentfault.com/questions/newest"

number.toFixed()   // "12346"
number.toFixed(3)  // "12345.679"
number.toFixed(6)  // "12345.678900"

typeof 3    // "number"
typeof "333"  // "string"
typeof false  // "boolean"

typeof new Date()  // "object"
typeof []      // "object"
typeof {}      // "object"
typeof null     // "object"   

toString instanceof Function
// true
(new Date) instanceof Date
// true
[] instanceof Object
// true
[] instanceof Array
// true

var toString = Object.prototype.toString;

toString.call(new Date)  // "[object Date]"
toString.call(new Array)  // "[object Array]"
toString.call(new Object) // "[object Object]"
toString.call(new Number) // "[object Number]"
toString.call(new String) // "[object String]"
toString.call(new Boolean) // "[object Boolean]"

//Shape - superclass
function Shape() {
 this.x = 0;
 this.y = 0;
}

Shape.prototype.move = function(x, y) {
  this.x += x;
  this.y += y;
  console.info("Shape moved.");
};

// Rectangle - subclass
function Rectangle() {
 Shape.call(this); //call super constructor.
}

Rectangle.prototype = Object.create(Shape.prototype);

var rect = new Rectangle();

rect instanceof Rectangle //true.
rect instanceof Shape //true.

rect.move(1, 1); //Outputs, "Shape moved."