《JavaScript高级程序设计》读书笔记(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"]

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