Uncovering the deepest levels of nested arrays and objects in JavaScript without any fancy libraries - a step-by-step guide!

Question

Uncovering the deepest levels of nested arrays and objects in JavaScript without any fancy libraries - a step-by-step guide!

I have been struggling to find a solution to a seemingly simple problem. Despite searching through various sites and resources, I have not been able to figure out how to iterate over the innermost levels of a doubly nested data structure. I have tried using methods like forEach() and map() without any success.

Here is some background information on the data I am working with. The data provided below is extracted from an array that contains information about two retail stores. Each store object includes a property called visits, which stores an array of visit objects. Each visit object is uniquely identified by a visit date and includes a values property that holds an array of transactions, such as purchases or returns, made during that visit. In the complete dataset, the number of transactions can vary significantly from one date to another.

The specific tasks I need assistance with are as follows: (a) Change the property key to visitDate, (b) Rename the property values to transactions, (c) Remove 8 unnecessary properties (from storeID to storeVisitDate), while keeping the action and dollarAmount properties, and (d) Update the property dollarAmount to dollars.

I would greatly appreciate any help that can be provided. Thank you.

 [ ... ]

javascript arrays object nested

Answer 1

Answer №1

That's spot on! Utilizing the .map() method can accomplish most of the tasks at hand. Thanks to the new ES6 standard, a lot of the processes have been simplified. The function provided below enables you to achieve your objectives without altering the original data:

array.map(store => {
  // Create a new object that retains all the store information, while updating the visits key in a new object
  return Object.assign({}, store, {
    // Iterate over the visits array, updating the key to visitDate
    visits: store.visits.map(({ key: visitDate, values }) => {
      return {
        // Create an object with visit date
        visitDate,
        // Perform destructuring to create objects of action and dollars
        transactions: values.map(({ action, dollarAmount: dollars }) => ({ action, dollars }))
      };
    })
  });
});

Answer 2

That's spot on! Utilizing the .map() method can accomplish most of the tasks at hand. Thanks to the new ES6 standard, a lot of the processes have been simplified. The function provided below enables you to achieve your objectives without altering the original data:

array.map(store => {
  // Create a new object that retains all the store information, while updating the visits key in a new object
  return Object.assign({}, store, {
    // Iterate over the visits array, updating the key to visitDate
    visits: store.visits.map(({ key: visitDate, values }) => {
      return {
        // Create an object with visit date
        visitDate,
        // Perform destructuring to create objects of action and dollars
        transactions: values.map(({ action, dollarAmount: dollars }) => ({ action, dollars }))
      };
    })
  });
});

Answer 3

Answer №2

(Check out the working example on jsFiddle here - just open the JS console to view the converted data set)

Here are a few key points regarding the solution provided below:

It has the capability to handle data sets with more keys than the sample provided. This ensures flexibility for complex data structures.

It predominantly utilizes the "map" function instead of manual array iteration for improved code readability.

// Iterates over all stores
stores.map(function(store) {
  // Within each store, iterates over all visits
  store.visits.map(function(visit) {
    // Renames 'key' to 'visitDate' and 'values' to 'transactions'
    // Then removes the old names ('key' and 'values')
    visit.visitDate = visit.key;
    visit.transactions = visit.values;
    delete visit.key;
    delete visit.values;

    // Replaces each transaction with a simplified map containing only 'action' and 'dollars'
    visit.transactions = visit.transactions.map(function(tx) {
      return {
        action: tx.action,
        dollars: tx.dollarAmount
      };
    });
  });
});

It's worth noting that map() is supported in IE9 and newer.

Answer 4

(Check out the working example on jsFiddle here - just open the JS console to view the converted data set)

Here are a few key points regarding the solution provided below:

It has the capability to handle data sets with more keys than the sample provided. This ensures flexibility for complex data structures.

It predominantly utilizes the "map" function instead of manual array iteration for improved code readability.

// Iterates over all stores
stores.map(function(store) {
  // Within each store, iterates over all visits
  store.visits.map(function(visit) {
    // Renames 'key' to 'visitDate' and 'values' to 'transactions'
    // Then removes the old names ('key' and 'values')
    visit.visitDate = visit.key;
    visit.transactions = visit.values;
    delete visit.key;
    delete visit.values;

    // Replaces each transaction with a simplified map containing only 'action' and 'dollars'
    visit.transactions = visit.transactions.map(function(tx) {
      return {
        action: tx.action,
        dollars: tx.dollarAmount
      };
    });
  });
});

It's worth noting that map() is supported in IE9 and newer.

Answer 5

Answer №3

To update property names, you can simply create a new property with the desired name and the same value, then use the delete operator to remove the old property.

In this case, it would be more organized to consolidate properties b, c, and d by leveraging the map() function to create a new array of optimized transactions and assign it to the updated transactions property.

// Function to update data properties
function modifyData(entries) {
  // Loop through each entry and update property names
  for (var iEntry = 0; iEntry < entries.length; iEntry++) {
    var entry = entries[iEntry];

    for (var iVisit = 0; iVisit < entry.visits.length; iVisit++) {
      var visit = entry.visits[iVisit];

      // Update property key to visitDate
      // Create a new property with the same value and then delete the old property
      visit.visitDate = visit.key;
      delete visit.key;

      // Update property values to transactions
      // Create a new property with the same value and then delete the old property
      // Delete redundant properties and rename specific properties
      visit.transactions = visit.values.map(function(transaction) {
        return {
          action: transaction.action,
          dollars: transaction.dollarAmount
        }
      });
      delete visit.values;
    }
  }

  console.log(entries);
}

var entries = [
 // Sample data entries here
];

modifyData(entries);

Answer 6

To update property names, you can simply create a new property with the desired name and the same value, then use the delete operator to remove the old property.

In this case, it would be more organized to consolidate properties b, c, and d by leveraging the map() function to create a new array of optimized transactions and assign it to the updated transactions property.

// Function to update data properties
function modifyData(entries) {
  // Loop through each entry and update property names
  for (var iEntry = 0; iEntry < entries.length; iEntry++) {
    var entry = entries[iEntry];

    for (var iVisit = 0; iVisit < entry.visits.length; iVisit++) {
      var visit = entry.visits[iVisit];

      // Update property key to visitDate
      // Create a new property with the same value and then delete the old property
      visit.visitDate = visit.key;
      delete visit.key;

      // Update property values to transactions
      // Create a new property with the same value and then delete the old property
      // Delete redundant properties and rename specific properties
      visit.transactions = visit.values.map(function(transaction) {
        return {
          action: transaction.action,
          dollars: transaction.dollarAmount
        }
      });
      delete visit.values;
    }
  }

  console.log(entries);
}

var entries = [
 // Sample data entries here
];

modifyData(entries);

Answer 7

Answer №4

Let's assume your array is named array, here is a suggestion:

array.forEach(function(item, index, array) {
   item.data = item.data.map(function(dataItem, index, array) {
      dataItem.visitDate = dataItem.timestamp;
      delete dataItem.timestamp;
      dataItem.transactions = dataItem.values.map(function(value, index, array) {
         return {action: value.task, amount: value.money};
      });
      delete dataItem.values;
      return dataItem;
   });
});

Answer 8

Let's assume your array is named array, here is a suggestion:

array.forEach(function(item, index, array) {
   item.data = item.data.map(function(dataItem, index, array) {
      dataItem.visitDate = dataItem.timestamp;
      delete dataItem.timestamp;
      dataItem.transactions = dataItem.values.map(function(value, index, array) {
         return {action: value.task, amount: value.money};
      });
      delete dataItem.values;
      return dataItem;
   });
});

Answer 9

Answer №5

Given that this is 'data' rather than in-memory objects, it seems likely that you extracted it from JSON using the JSON.parse method. (If not, you can still achieve the same by initially using JSON.stringify)

Were you aware that JSON.parse allows you to pass in a function to customize the parsing process? https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/parse

Therefore...

updatedData = JSON.parse(dataString, function(key, value) {
 if(key === "key") {this.visitDate = value; return;}
 if(key === "values"){this.transactions = value; return;}
 if(key === "somethingYouDontWant"){return;}
 //etc...
 return value;
})

Answer 10

Given that this is 'data' rather than in-memory objects, it seems likely that you extracted it from JSON using the JSON.parse method. (If not, you can still achieve the same by initially using JSON.stringify)

Were you aware that JSON.parse allows you to pass in a function to customize the parsing process? https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/parse

Therefore...

updatedData = JSON.parse(dataString, function(key, value) {
 if(key === "key") {this.visitDate = value; return;}
 if(key === "values"){this.transactions = value; return;}
 if(key === "somethingYouDontWant"){return;}
 //etc...
 return value;
})

Answer 11

Answer №6

Here is a customized approach using the Array.map() method along with the delete operator:

let propertiesToDelete = ["prop1", "prop2", "prop3"];

// arrayData represents the original array
arrayData.map(function(data){
    data['subData'].map(function(subData){
        subData['newProperty'] = subData['oldProperty'];
        delete subData['oldProperty'];
        
        subData['nestedData'].map(function(nestedData){
            nestedData['newValue'] = nestedData['originalValue'];
            delete nestedData['originalValue'];

            propertiesToDelete.forEach(function(prop){
                delete nestedData[prop];
            });
        });

        subData['modifiedData'] = subData['nestedData'];
        delete subData['nestedData'];
    });
});

Answer 12

Here is a customized approach using the Array.map() method along with the delete operator:

let propertiesToDelete = ["prop1", "prop2", "prop3"];

// arrayData represents the original array
arrayData.map(function(data){
    data['subData'].map(function(subData){
        subData['newProperty'] = subData['oldProperty'];
        delete subData['oldProperty'];
        
        subData['nestedData'].map(function(nestedData){
            nestedData['newValue'] = nestedData['originalValue'];
            delete nestedData['originalValue'];

            propertiesToDelete.forEach(function(prop){
                delete nestedData[prop];
            });
        });

        subData['modifiedData'] = subData['nestedData'];
        delete subData['nestedData'];
    });
});

Answer 13

Answer №7

Presented here is an alternative approach, featuring code that is easily understandable but lacks optimization.

let obj = {}, key;
data.forEach((item) => {
  item.visits.forEach((visit) => {
    visit.visitDate = visit.key; 
    delete visit.key;
    visit.transactions = [];
    visit.values.forEach((value) => {
      obj = {};
      for (key in value) {
        if (value.hasOwnProperty(key) && retain.indexOf(key) > -1) {
          obj[key] = value[key];
        }
      }
      visit.transactions.push(obj);
    });
    delete visit.values;
  });
console.log(item);
});

Answer 14

Presented here is an alternative approach, featuring code that is easily understandable but lacks optimization.

let obj = {}, key;
data.forEach((item) => {
  item.visits.forEach((visit) => {
    visit.visitDate = visit.key; 
    delete visit.key;
    visit.transactions = [];
    visit.values.forEach((value) => {
      obj = {};
      for (key in value) {
        if (value.hasOwnProperty(key) && retain.indexOf(key) > -1) {
          obj[key] = value[key];
        }
      }
      visit.transactions.push(obj);
    });
    delete visit.values;
  });
console.log(item);
});

Answer 15

Answer №8

This code is written in pure JavaScript without the use of any external library. It utilizes a simple mapping technique:

 var result = input.map(function(data){
      data.subItems = data.subItems.map(function (item){
        return {
          date: item.date,
          details: item.values.map(function(value){
            return {
              action: value.action,
              amount: value.amount
            };
          })
        };
      });
      return data;
    });

Answer 16

This code is written in pure JavaScript without the use of any external library. It utilizes a simple mapping technique:

 var result = input.map(function(data){
      data.subItems = data.subItems.map(function (item){
        return {
          date: item.date,
          details: item.values.map(function(value){
            return {
              action: value.action,
              amount: value.amount
            };
          })
        };
      });
      return data;
    });

Uncovering the deepest levels of nested arrays and objects in JavaScript without any fancy libraries - a step-by-step guide!

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

Answer №6

Answer №7

Answer №8

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