How can I get one property name in a javascript object?

Question

Possible Duplicate:
Pick random property from a Javascript object

suppose I have a javascript object:

Config.UI.Area = {
        "uuid": {
            "_type": "string"
        },
        "frame": {
            "_type": "rect"
        },
        "zIndex": {
            "_type": "string"
        }
 }

then I want get each of the property's name,like "uuid","frame","zIndex" by using for loop:

var prop=config.ui.area;
var arr=new Array()
for(var i in prop){
    //do something with prop[i]?
    //arr.push(prop[i].....)?
}

I can not directly use prop[i],it would return me an object,how can I just get it's name?

dup: http://stackoverflow.com/questions/3068534/getting-javascript-object-key-list — Alexander, Apr 05 '12 at 06:21

KooiInc · Accepted Answer · 2012-04-05T06:26:34.240

5

This would give you an array of property names:

for(var name in prop){
    //do something with prop[name]?
    arr.push(name);
}

It would also give you the names of 'native' properties of the Object object. To avoid that, use the hasOwnProperty method:

for(var name in prop){
    if (prop.hasOwnPropery(name) {
     arr.push(name);
    }
}

edited Apr 05 '12 at 06:26

answered Apr 05 '12 at 06:18

KooiInc

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score 1 · Answer 2 · answered Apr 05 '12 at 06:22

1

Below is how you iterate property and get corresponding value

var prop=config.ui.area;
var arr=new Array()
for(var i in prop){
    //do something with prop[i]?
    var propertyName = i;
    var propertyValue = prop[i];
}

answered Apr 05 '12 at 06:22

Ramesh

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score 0 · Answer 3 · answered Apr 05 '12 at 06:26

prop (and Config.UI.Area) is an object ( not an array of object ). So you cannot do prop[i].

Try this,

   var obj = {
           "uuid": {
               "_type": "string"
           },
           "frame": {
               "_type": "rect"
           },
           "zIndex": {
               "_type": "string"
           }
    }

   var prop = obj;
   var arr=[];
   for(var i in prop){
       if(i.hasOwnProperty){
         arr.push(i);
       }
   }
   console.log(arr);

score 0 · Answer 4 · answered Apr 05 '12 at 06:55

To get to the name of an object's property in a loop use:

for(var propertyName in myObject) {
  if(myObject.hasOwnProperty(propertyName) {
    console.log(propertyName); // will be uuid, frame or zIndex
  }
}

To get to properties of the sub objects, use

for(var propertyName in myObject) {
  if(myObject.hasOwnProperty(propertyName) {
    var subObject = myObject[propertyName];
    console.log(subObject._type);
           // will string or rect based on your sample code
  }
}

Using the hasOwnProperty in a loop through an object is a good idea as it will filter out properties of the object that are inherited via its prototype.

How can I get one property name in a javascript object?

4 Answers4