JavaScript高级程序设计读书笔记之九本地对象Array_javascript技巧

//two
var aValues=new Array(20);

//three
var aColors=new Array();
aColors[0]="red";
aColors[1]="green";
aColors[2]="blue";

//four
var aColors=new Array("red","green","blue");

//five
var aColors=["red","green","blue"];

join && split
join:连接字符串
代码如下:
var aColors=["red","green","blue"];
alert(aColors.join(","));//outputs "red,green,blue"
alert(aColors.join("-spring-"));//outputs "red-spring-green-spring-blue"
alert(aColors.join("]["));//outputs "red][green][blue"

split:分拆字符串
代码如下:
var sColors="red,green,blue";
var aColors=sColors.split(",");//outputs ["red", "green", "blue"]
var redColors=aColors[0].split("");//outputs ["r", "e", "d"]

concat && slice
concat:追加数组
代码如下:
var aColors=["red","green","blue"];
var aColors2=aColors.concat("yellow","purple");
alert(aColors);//outputs ["red", "green", "blue"]
alert(aColors2);//outputs ["red", "green", "blue", "yellow", "purple"]

slice:返回具有特定项的新数组
代码如下:
var aColors=["red","green","blue","yellow","purple"];
var aColors2=aColors.slice(1);//outputs ["green","blue","yellow","purple"]
var aColors3=aColors.slice(1,4);//outputs ["green","blue","yellow"]

push && pop
跟栈一样，Array提供了push和pop方法，push方法用于在Array结尾添加一个或多个项，pop用于删除最后一个数组项，返回它作为函数值
代码如下:
var stack=new Array;
stack.push("red");
stack.push("green");
stack.push("blue");
alert(stack);//outputs ["red","green","blue"]
var vItem=stack.pop();
alert(vItem);//outputs ["blue"]
alert(stack);//otputs ["red","green"]

shift && unshift
shift:删除数组中第一项，将其作为函数返回值，unshift:把一个项放在数组的第一个位置，然后把余下的项向下移动一个位置
代码如下:
var aColors=["red","green","blue"];
var vItem=aColors.shift();
alert(aColors);//outputs ["green","blue"]
alert(vItem);//outputs ["red"]
aColors.unshift("black");
alert(aColors);//outputs ["black","green","blue"]

reverse && sort
reverse:颠倒数组项的顺序，sort:按数组项的值升序排列(首先要调用toString()方法，将所有值转换成字符串)
代码如下:
var aColors=["blue","green","red"];
aColors.reverse();
alert(aColors);//outputs ["red","green","blue"]
aColors.sort();
alert(aColors);//outputs ["blue","green","red"]

注意：
代码如下:
var aColors=[3,32,2,5];
aColors.sort();
alert(aColors);//outputs [2,3,32,5]

这是因为数字被转换成字符串，然后按字符代码进行比较的。

splice
splice:把数据项插入数组的中部

1、用作删除：只要声明两个参数，第一个参数为要删除的第一个项的位置，第二个参数为删除项的个数
代码如下:
var aColors=["red","green","blue","yellow"];
aColors.splice(0,2);
alert(aColors);//outputs ["blue", "yellow"]

2、用作插入：声明三个或以上参数(第二个参数为0)就可以把数据插入指定位置，第一个参数为地始位置，第二个参数为0，第三个及以上参数为插入项
代码如下:
var aColors=["red","green","blue","yellow"];
aColors.splice(2,0,"black","white");
alert(aColors);//outputs ["red","green","black","white","blue", "yellow"]

3、用作删除并插入：声明三个或以上参数(第二个参数为不0)就可以把数据插入指定位置，第一个参数为地始位置，第二个参数为要删除的项的个数，第三个及以上参数为插入项
代码如下:
var aColors=["red","green","blue","yellow"];
aColors.splice(2,1,"black","white");
alert(aColors);//outputs ["red","green","black","white", "yellow"]