使用闭包封装一个汽车对象，可以获取汽车状态
var Car = (function(){
var speed;
function setSpeed(n){
speed = n;
}
function getSpeed(){
return speed;
}
function accelerate(){
speed += 10;
}
function decelerate(){
speed -= 10;
}
function getStatus(){
if(speed>0){
return 'running';
}else{
return 'stop';
}
}
return {
'setSpeed': setSpeed,
'getSpeed': getSpeed,
'accelerate':accelerate,
'decelerate':decelerate,
'getStatus':getStatus
}
})();
Car.setSpeed(30);
Car.getSpeed(); //30
Car.accelerate();
Car.getSpeed(); //40;
Car.decelerate();
Car.decelerate();
Car.getSpeed(); //20
Car.getStatus(); // 'running';
Car.decelerate();
Car.decelerate();
Car.getStatus(); //'stop';
