How to Check If Object Property Exists with a Variable Holding the Property Name?

When working with JavaScript, it is common to come across situations where you need to check if an object property exists. In some cases, you may have the property name stored in a variable and need to determine if the property exists using that variable. In this blog post, we will explore different ways to accomplish this task.

Method 1: Using the ‘in’ Operator

The ‘in’ operator can be used to check if a property exists in an object. To use it with a variable holding the property name, you can concatenate the object name with the variable using square brackets. Here’s an example:

// Object with properties
const myObject = {
  name: 'John',
  age: 30,
};

// Variable holding property name
const propertyName = 'name';

// Checking if property exists
const propertyExists = propertyName in myObject;

console.log(propertyExists); // Output: true

Method 2: Using the ‘hasOwnProperty’ Method

The ‘hasOwnProperty’ method can also be used to check if a property exists in an object. This method returns a boolean value indicating whether the object has the specified property as a direct property. Here’s an example:

// Object with properties
const myObject = {
  name: 'John',
  age: 30,
};

// Variable holding property name
const propertyName = 'name';

// Checking if property exists
const propertyExists = myObject.hasOwnProperty(propertyName);

console.log(propertyExists); // Output: true

Method 3: Using the ‘typeof’ Operator

Another approach is to use the ‘typeof’ operator to check if the property exists. By accessing the property using the variable, you can compare its type against ‘undefined’. If the type is ‘undefined’, it means the property does not exist. Here’s an example:

// Object with properties
const myObject = {
  name: 'John',
  age: 30,
};

// Variable holding property name
const propertyName = 'name';

// Checking if property exists
const propertyExists = typeof myObject[propertyName] !== 'undefined';

console.log(propertyExists); // Output: true

These are three different methods you can use to check if an object property exists with a variable holding the property name. Choose the method that best suits your requirements and coding style.