如何对javascript中的对象进行计数

Question

这是我的代码，我想要计算其中的对象数量。

使用eval函数，我能够获得元素，但不知道如何计算其中的对象总数。有人能帮帮我吗？？

var txt = '{
    "employees": [{
        "a": "wkn",
        "d": "Wipro Technologies \u2013 IT Services, Product Engineering Solutions, Technology Infrastructure Services, Business Process Outsourcing, Consulting Services",
        "n": "",
        "u": "http://wipro.com/",
        "t": ["outsourcing", "offshore", "india"],
        "dt": "2009-06-26T10:26:02Z"
    }, {
        "a": "shaktimaan",
        "d": "Wipro Technologies \u2013 IT Services, Product Engineering Solutions, Technology Infrastructure Services, Business Process Outsourcing, Consulting Services",
        "n": "Wipro Technologies is the No 1 provider of integrated business, technology and process solutions on a global delivery platform.",
        "u": "http://wipro.com/",
        "t": ["Indian", "IT", "Services", "Companies"],
        "dt": "2011-09-16T17:31:25Z"
    }, {
        "a": "tonemcd",
        "d": "Offshore Outsourcing | IT Services",
        "n": "",
        "u": "http://wipro.com/",
        "t": ["outsourcing", "IT"],
        "dt": "2007-11-04T03:53:18Z"
    }]
}'; //added \n for readability

var obj = eval ("(" + txt + ")");



document.getElementById("fname").innerHTML=obj.employees[1].a 
document.getElementById("lname").innerHTML=obj.employees[1].u 

这是我得到的回应：

First Name: shaktimaan
Last Name: http://wipro.com/

我能够获取elemtns，但我需要对象计数。

Answer 1

您可以使用length

obj.employees.length

这是JSFiddle：http://jsfiddle.net/wavXY/3/

我推荐使用JSON.parse而不是eval。请通过此链接了解更多详细信息：http://www.json.org/js.html

Answer 2

作为一个JS新手，看着你的员工数组，我自己想知道它是如何被遍历的。我做了一些实验，也许这不是最有效的方法，但它帮助我理解了如何遍历和计算这样的东西。

这就是问题所在：http://jsfiddle.net/bSMQn/

var txt = '{"employees":[{"a": "wkn", "d": "Wipro Technologies \u2013 IT Services, Product Engineering Solutions, Technology Infrastructure Services, Business Process Outsourcing, Consulting Services", "n": "", "u": "http://wipro.com/", "t": ["outsourcing", "offshore", "india"], "dt": "2009-06-26T10:26:02Z"}, {"a": "shaktimaan", "d": "Wipro Technologies \u2013 IT Services, Product Engineering Solutions, Technology Infrastructure Services, Business Process Outsourcing, Consulting Services", "n": "Wipro Technologies is the No 1 provider of integrated business, technology and process solutions on a global delivery platform.", "u": "http://wipro.com/", "t": ["Indian", "IT", "Services", "Companies"], "dt": "2011-09-16T17:31:25Z"}, {"a": "tonemcd", "d": "Offshore Outsourcing | IT Services", "n": "", "u": "http://wipro.com/", "t": ["outsourcing", "IT"], "dt": "2007-11-04T03:53:18Z"}]}';

var obj = eval ("(" + txt + ")");
var i =0;
for (;i<obj.employees.length;i++)
{
    document.writeln("Employee " + i+":<br/><br/>");
    var j = 0;
    for(v in obj.employees[i])
    {
        j++;
        document.writeln(v + " => " + obj.employees[i][v] +"<br/>");
    }
    document.writeln("<b>Count:" + j +"</b>");
    document.writeln("<hr/><br/>");

}

输出

Employee 0:

a => wkn
d => Wipro Technologies – IT Services, Product Engineering Solutions, Technology Infrastructure Services, Business Process Outsourcing, Consulting Services
n => 
u => http://wipro.com/
t => outsourcing,offshore,india
dt => 2009-06-26T10:26:02Z
Count:6

Employee 1:

a => shaktimaan
d => Wipro Technologies – IT Services, Product Engineering Solutions, Technology Infrastructure Services, Business Process Outsourcing, Consulting Services
n => Wipro Technologies is the No 1 provider of integrated business, technology and process solutions on a global delivery platform.
u => http://wipro.com/
t => Indian,IT,Services,Companies
dt => 2011-09-16T17:31:25Z
Count:6

....etc

希望能有所帮助。