11.8练习
编写Card对象的构造函数，添加suit属性（方块、红心、黑桃、梅花）和face属性（A，2，3，…，王），添加方法来设置suit和face。试添加一个shuffle方法来设置suit和face属性，表示洗牌之后的状态。（提示：使用第5章介绍的Math.random()方法。）
用关键字prototype扩展JavaScript的Date对象，添加一个方法getYesterday()，返回Date对象所表示的日期的前一天的名称。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<script>
var suits=["方块","红心","黑桃","梅花"];
var faces=['A','2','3','4','5','6','7','8','9','10','J','Q','K','王'];
function card(){
this.suit="";
this.face="";
this.setSuit=function(newSuit){
this.suit=newSuit;
}
this.setFace=function(newFace){
this.face=newFace;
}
this.shuffle=function(){
var snum=Math.floor(Math.random()*3);
this.suit=suits[snum];
var fnum=Math.floor(Math.random()*14);
this.face=faces[fnum];
}
}
var book1=new card();
book1.setSuit("方块");
book1.setFace("2");
var book2=new card();
book2.shuffle();
alert("book1 is "+book1.suit+book1.face+"\nbook2 is "+book2.suit+book2.face);
//日期前一天
Date.prototype.getYesterday=function(){
var now=new Date();
var yester=now-1000*60*60*24;
var yesterday=new Date(yester);
return yesterday.toLocaleString();
}
var yesterday=new Date().getYesterday();
//alert("yesterday is "+yesterday);
</script>
</body>
</html>
