JavaScript高级程序设计 读书笔记之九 本地对象Array

创建Array对象

//one 
var aValues=new Array(); //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

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

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

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

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

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

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)

var aColors=["blue","green","red"]; 
aColors.reverse(); 
alert(aColors);//outputs ["red","green","blue"] 
aColors.sort(); 
alert(aColors);//outputs ["blue","green","red"]

注意：

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

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

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

var aColors=["red","green","blue","yellow"]; 
aColors.splice(2,1,"black","white"); 
alert(aColors);//outputs ["red","green","black","white", "yellow"]