JavaScript数组

2018-10-26 javaScript PV:

JavaScript数组

复习一下数组，发现有些方法都忘记了

定义数组的方式

采用直接量创建

var MyArray = [];//创建空数组

var MyArray = [1,2,3];//创建数字型数组

var MyArray = [“A”,”B”,”C”];//创建字符型数组

var MyArray = [{id:1},{id:2},{id:3}];//创建对象型数组
采用构造函数创建

var MyArray = new Array();
MyArray[0] = 0;
MyArray[1] = “A”;

var MyArray = new Array(5);

var MyArray = new Array(5,4,3,2,1);

属性

constructor

描述：返回对创建此对象的数组函数的引用。

应用1：用于判断元素类型

exp：



var test=new Array();

if (test.constructor==Array)
{
	document.write("This is an Array");
}
if (test.constructor==Boolean)
{
	document.write("This is a Boolean");
}
if (test.constructor==Date)
{
	document.write("This is a Date");
}
if (test.constructor==String)
{
	document.write("This is a String");
}

输出：

This is an Array

应用2：用于获取构造函数的原形

exp:

function employee(name,job,born)
{
    this.name=name;
    this.job=job;
    this.born=born;
}

var bill=new employee("Bill Gates","Engineer",1985);

document.write(bill.constructor);

输出：

function employee(name, job, born)
{
    this.name = name; 
    this.job = job; 
    this.born = born;
}

length

描述：设置或返回数组中元素的数目

应用：设置或返回数组中元素的数目

exp：

var arr = new Array(3)
arr[0] = "John"
arr[1] = "Andy"
arr[2] = "Wendy"

document.write("Original length: " + arr.length)
document.write("<br />")

arr.length=5
document.write("New length: " + arr.length)

输出：

Original length: 3
New length: 5

prototype

描述：使您有能力向对象添加属性和方法

应用：向对象添加属性和方法

exp:

Post author: Michael Wang
Post link: http://yoursite.com/2018/10/26/JavaScript数组/
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