Is Object Empty - Practice Coding Problems

Is Object Empty - Problem

JavaScript Easy

In JavaScript development, you'll often need to check if an object or array is empty before processing it. This is a fundamental operation that helps prevent errors and unnecessary computations.

Given a JavaScript object or array (the result of JSON.parse), determine whether it contains any data:

An empty object {} contains no key-value pairs
An empty array [] contains no elements

Your task: Return true if the input is empty, false otherwise.

Example: {} → true, {"a": 1} → false, [] → true, [1, 2] → false

Input & Output

example_1.js — Empty Object

$ Input: {}

› Output: true

💡 Note: The object contains no key-value pairs, so it's considered empty

example_2.js — Non-empty Object

$ Input: {"x": 5, "y": 42}

› Output: false

💡 Note: The object has 2 properties (x and y), so it's not empty

example_3.js — Empty Array

$ Input: []

› Output: true

💡 Note: The array contains no elements, so it's considered empty

example_4.js — Non-empty Array

$ Input: [null, false, 0]

› Output: false

💡 Note: Even though the elements are falsy values, the array still contains 3 elements, so it's not empty

Constraints

The input is guaranteed to be a valid JSON object or array
Objects can have nested objects/arrays as values
Arrays can contain any valid JSON values including null, false, and 0
Maximum depth of nesting: 100 levels

Visualization

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Understanding the Visualization

Identify Container

Determine if checking an object {} or array []

Check Size Label

Look at the built-in size indicator (length/keys count)

Instant Result

Return true if size is 0, false otherwise

Key Takeaway

🎯 Key Insight: Use built-in size properties instead of manual iteration for instant O(1) empty checks

Asked in

G Google 24 a Amazon 18 f Meta 15 ⊞ Microsoft 12

The optimal solution uses built-in methods to check container size in O(1) time. For objects, use Object.keys(obj).length === 0; for arrays, use obj.length === 0. This avoids unnecessary iteration and provides instant results.

Common Approaches

Approach	Time	Space	Notes
✓ Brute Force (Manual Iteration)	O(1)	O(1)	Manually iterate through all properties/elements to check if any exist

Brute Force (Manual Iteration) — Algorithm Steps

Check if input is an array using Array.isArray()
If array: iterate through indices and return false if any element exists
If object: use for...in loop to check for any enumerable property
Return true only if no properties/elements were found

Visualization

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Step-by-Step Walkthrough

Identify Container Type

Determine if we're checking an array or object

Start Iteration

Begin checking each slot/property one by one

First Item Check

If any item found, immediately return false

Complete Scan

If no items found after full scan, return true

Code -

solution.c — C

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <cjson/cJSON.h>

int isEmpty(cJSON *json) {
    if (cJSON_IsArray(json)) {
        int size = cJSON_GetArraySize(json);
        for (int i = 0; i < size; i++) {
            return 0; // Found element, not empty
        }
        return 1; // No elements found
    }
    
    if (cJSON_IsObject(json)) {
        cJSON *item = json->child;
        if (item != NULL) {
            return 0; // Found property, not empty
        }
        return 1; // No properties found
    }
    
    return 0; // Invalid input
}

int main() {
    char input[1000];
    fgets(input, sizeof(input), stdin);
    cJSON *json = cJSON_Parse(input);
    printf("%s\n", isEmpty(json) ? "true" : "false");
    cJSON_Delete(json);
    return 0;
}

Time & Space Complexity

Time Complexity

⏱️

O(1)

Despite the loop, we return immediately upon finding the first property, making it O(1) for non-empty inputs. For empty inputs, it's still O(1) as there are no properties to iterate.

✓ Linear Growth

Space Complexity

O(1)

No additional space needed beyond variables for iteration

✓ Linear Space

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Smart Actions

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Input & Output

Constraints

Visualization

Related Problems

Common Approaches

Brute Force (Manual Iteration) — Algorithm Steps

Visualization

Code -

Time & Space Complexity

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