What is the best way to retrieve values from a JSON object without knowing the specific key?

Question

What is the best way to retrieve values from a JSON object without knowing the specific key?

Given the JSON object below, I am looking to extract specific values using JavaScript in my browser's dev console. However, I am not sure how to loop through an array of arrays. Can anyone provide guidance on achieving this task?

var infoJSON;
for(key in myClass) {
  infoJSON = myClass[key];
  console.log(infoJSON);
}




var myClass= {
   "Subjects":"3",
   "Subject":{
      "maths":{
         "subject_id":"1",
         "subject_level":"easy",
         "marks":"90"
      },
      "english":{
         "subject_id":"2",
         "subject_level":"medium",
         "marks":"80"
      },
      "physics":{
         "subject_id":"3",
         "subject_level":"tough",
         "marks":"70"
      }
   },
   "Average": "80"
};

I am working on a JavaScript function that will display the total number of subjects, each subject with its marks, and the average marks in the browser console as shown below.

Subjects: 3
- maths (90)
- english (80)
- physics (70)
Average: 80

The goal is for the code to be dynamic and work with any JSON object following the same structure without hardcoding keys such as maths or physics.

javascript arrays json console.log

Answer 1

Answer №1

To determine what you are iterating in your class, you should check if the key is a string. If it is a string, you can print it directly. If it is not a string, iterate through its keys and then print them.

var myClass= {"Subjects":"3","Subject":{"maths":{"subject_id":"1","subject_level":"easy","marks":"90"},"english":{"subject_id":"2","subject_level":"medium","marks":"80"},"physics":{"subject_id":"3","subject_level":"tough","marks":"70"}},"Average":"80"};

for (let key in myClass) {
  let value = myClass[key];
  if (typeof value === 'string') {
    console.log( `${key}: ${value}` );
    continue;
  }
  console.log( Object.keys( value ).map( k => `- ${k} (${value[k].marks})` ).join('\n') );
}

// if you want it in one log output
console.log( Object.keys( myClass ).reduce( (result, key) => {
  if (typeof myClass[key] === 'object') {
    let value = myClass[key];
    return result.concat( Object.keys( value ).map( k => `- ${k} (${value[k].marks})` ) );
  }
  result.push( `${key}: ${myClass[key]}` );
  return result;
}, [] ).join('\n') );

Answer 2

To determine what you are iterating in your class, you should check if the key is a string. If it is a string, you can print it directly. If it is not a string, iterate through its keys and then print them.

var myClass= {"Subjects":"3","Subject":{"maths":{"subject_id":"1","subject_level":"easy","marks":"90"},"english":{"subject_id":"2","subject_level":"medium","marks":"80"},"physics":{"subject_id":"3","subject_level":"tough","marks":"70"}},"Average":"80"};

for (let key in myClass) {
  let value = myClass[key];
  if (typeof value === 'string') {
    console.log( `${key}: ${value}` );
    continue;
  }
  console.log( Object.keys( value ).map( k => `- ${k} (${value[k].marks})` ).join('\n') );
}

// if you want it in one log output
console.log( Object.keys( myClass ).reduce( (result, key) => {
  if (typeof myClass[key] === 'object') {
    let value = myClass[key];
    return result.concat( Object.keys( value ).map( k => `- ${k} (${value[k].marks})` ) );
  }
  result.push( `${key}: ${myClass[key]}` );
  return result;
}, [] ).join('\n') );

Answer 3

Answer №2

To achieve this, you can utilize basic for in, Object.keys().

Give this a try:

var myClass= {"Subjects":"3","Subject":{"maths":{"subject_id":"1","subject_level":"easy","marks":"90"},"english":{"subject_id":"2","subject_level":"medium","marks":"80"},"physics":{"subject_id":"3","subject_level":"tough","marks":"70"}},"Average":"80"};

for(key in myClass){
  if(myClass[key].constructor.toString().indexOf("Object") > 0){
      Object.keys(myClass[key]).forEach((k)=> {
        console.log(k +" - "+ myClass[key][k].marks);
      });
   } else{
    console.log(key +" - " +myClass[key]);
   }
}

Answer 4

To achieve this, you can utilize basic for in, Object.keys().

Give this a try:

var myClass= {"Subjects":"3","Subject":{"maths":{"subject_id":"1","subject_level":"easy","marks":"90"},"english":{"subject_id":"2","subject_level":"medium","marks":"80"},"physics":{"subject_id":"3","subject_level":"tough","marks":"70"}},"Average":"80"};

for(key in myClass){
  if(myClass[key].constructor.toString().indexOf("Object") > 0){
      Object.keys(myClass[key]).forEach((k)=> {
        console.log(k +" - "+ myClass[key][k].marks);
      });
   } else{
    console.log(key +" - " +myClass[key]);
   }
}

Answer 5

Answer №3

In this code snippet, the relationship between Subjects and Average is fixed which allows for hardcoded values. However, the other fields within the array require iteration to access:

var myClass= {
   "Subjects":"3",
   "Subject":{
      "maths":{
         "subject_id":"1",
         "subject_level":"easy",
         "marks":"90"
      },
      "english":{
         "subject_id":"2",
         "subject_level":"medium",
         "marks":"80"
      },
      "physics":{
         "subject_id":"3",
         "subject_level":"tough",
         "marks":"70"
      }
   },
   "Average": "80"
};
var infoJSON;
console.log('Subjects: ' + myClass['Subjects']);
for(key in myClass['Subject']) {
  console.log('- ' + key + ' (' + myClass['Subject'][key]['marks'] + ')');
}
console.log('Average: ' + myClass['Average']);

Answer 6

In this code snippet, the relationship between Subjects and Average is fixed which allows for hardcoded values. However, the other fields within the array require iteration to access:

var myClass= {
   "Subjects":"3",
   "Subject":{
      "maths":{
         "subject_id":"1",
         "subject_level":"easy",
         "marks":"90"
      },
      "english":{
         "subject_id":"2",
         "subject_level":"medium",
         "marks":"80"
      },
      "physics":{
         "subject_id":"3",
         "subject_level":"tough",
         "marks":"70"
      }
   },
   "Average": "80"
};
var infoJSON;
console.log('Subjects: ' + myClass['Subjects']);
for(key in myClass['Subject']) {
  console.log('- ' + key + ' (' + myClass['Subject'][key]['marks'] + ')');
}
console.log('Average: ' + myClass['Average']);

What is the best way to retrieve values from a JSON object without knowing the specific key?

Answer №1

Answer №2

Answer №3

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