Retrieving data from an object

Question

I have an object which looks like this.

{
 "class_details":{
                  "class_1":{student_4":"<name>","student_3":"<name>,student_2":"<name>","student_1":"<name>},
                  "class_2":{"student_1":"<name>},
                  "class_0":{student_2":"<name>","student_1":"<name>
                 }
}

I am trying to use a loop to iterate over the classes but I am not able find a perfect way to do it.

I cant do something like this,

for(int i=0; i < $scope.rounds.class_details.length;i++)
    console.log($scope.rounds.class_details.round_[i])

So i am doing this

for(int i=0; i < $scope.rounds.class_details.length;i++)
    console.log(Object.keys($scope.rounds.class_details)[i])

But here the class details do not come in an order and this matters in my case.

It would be great if there is an alternative similar to

 for(int i=0; i < $scope.rounds.class_details.length;i++)
        console.log($scope.rounds.class_details.round_[i])

or if there is a simple way to sort the JSON class details.

http://stackoverflow.com/questions/5467129/sort-javascript-object-by-key — Chris, Apr 17 '16 at 16:46
I will try this for sure but would would like to if I can read data like this $scope.rounds.class_details.round_{{0}} — Mukund Gandlur, Apr 17 '16 at 16:49

randominstanceOfLivingThing · Answer 1 · 2016-04-17T18:21:59.237

1

To get the keys in ascending order do:

 var class_details_keys = Object.keys($scope.rounds.class_details);
 class_details_keys = class_details_keys.sort(function(a,b) {return (+a.substring(6)) - (+b.substring(6));});
 for(int i=0, length = class_details_keys ; i < length;i++)
    console.log($scope.rounds.class_details[class_details_keys[i]]);

This will return your classes in ascending order by taking the substring after 'class_' and ordering them. You can't do a simple string comparison since "4" > "10" will return incorrect result.

edited Apr 17 '16 at 18:21

answered Apr 17 '16 at 17:01

randominstanceOfLivingThing

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Sort functions should return -1, 0, or +1, not a boolean. – Apr 17 '16 at 17:48

score 0 · Accepted Answer · answered Apr 17 '16 at 16:54

0

The simplest way to read data like you're hoping is the following:-

 for(int i=0; i < $scope.rounds.class_details.length;i++)
    console.log($scope.rounds.class_details["round_" + i]);

This is because you can access an objects property in two ways: -

Allows you to pass a dynamic value in (i.e. the i value)

object["property" + withVariable + "Name"]
Simple, readable way where you know the property.

object.propertyName

answered Apr 17 '16 at 16:54

Shakespeare

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I do not understand why `$scope.rounds.class_details` has a length. It is an object, not an array. – Apr 17 '16 at 17:21
I know, that's weird... It wouldn't have a length unless it is added as a property somewhere along the lines... Might be worth you double checking you're looping the number of class details correctly, @MukundGandlur (something like Object.keys($scope.rounds.class_details).length should work in IE9+) – Shakespeare Apr 17 '16 at 20:10

score 0 · Answer 3 · answered Apr 17 '16 at 16:58

First, fix json. NOTE: there are some quotes missing in the original code.

  "class_details":{
      "class_1":{
          "student_4":"<name>",
          "student_3":"<name>",
          "student_2":"<name>",
          "student_1":"<name>"
       },
       "class_2":{
           "student_1":"<name>"
       },
       "class_0":{
           "student_2":"<name>",
           "student_1":"<name>"
       }
   }

Followed to this:

 //parse to json. Assume the 
      //'body' is the json data received

 //if there is data in body
 if(body){
    //parse body
    var parsed_body= JSON.parse(body);

    //your data
    var class_details = parsed_body.class_details;
    var class_2_student_1 = parsed_body.class_details.class_2.student_1;

    //if you want to print json directly to the front-end, 
    //then Object Object may be printed out. to prevent this, 
    //one could use .toString() to convert Object to String.
 }

 else{}//do something if no data in the body

Retrieving data from an object

3 Answers3