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Flatten JavaScript objects into a single-depth Object

Last Updated : 14 Oct, 2025
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Given a nested JavaScript object, the task is to flatten the object and pull out all the values to a single depth. If the values are already at a single depth then it returns the result unaltered.

[Approach]: Using typeof()

  • The typeof() method is used in the script to check the type of JavaScript variable.
  • The Variable parameter represents the input value to be checked, and the method returns a string indicating the type of that variable.

How it works:

1. We make a function called flatten object which takes input of an object and returns an object.

2. Loop through the object and check the type of the current property:

  • If it is of type Object and it is not an Array, recursively call the function again.
  • Otherwise, store the value in the result.

3. Return the object.

JavaScript 
// Declare an object
let ob = {
    Company: "GeeksforGeeks",
    Address: "Noida",
    contact: +91-999999999,
    mentor: {
        HTML: "GFG",
        CSS: "GFG",
        JavaScript: "GFG"
    }
};

// Declare a flatten function that takes 
// object as parameter and returns the 
// flatten object
const flattenObj = (ob) => {

    // The object which contains the
    // final result
    let result = {};

    // loop through the object "ob"
    for (const i in ob) {

        // We check the type of the i using
        // typeof() function and recursively
        // call the function again
        if ((typeof ob[i]) === 'object' && !Array.isArray(ob[i])) {
            const temp = flattenObj(ob[i]);
            for (const j in temp) {

                // Store temp in result
                result[i + '.' + j] = temp[j];
            }
        }

        // Else store ob[i] in result directly
        else {
            result[i] = ob[i];
        }
    }
    return result;
};

console.log(flattenObj(ob));

Output
{
  Company: 'GeeksforGeeks',
  Address: 'Noida',
  contact: -999999908,
  'mentor.HTML': 'GFG',
  'mentor.CSS': 'GFG',
  'mentor.JavaScript': 'GFG'
}

S

shubhamx
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