How do I check if a key exists in an object in JavaScript?
Antek N

To check if a key exists in an object in JavaScript, you can use various techniques. Here's a step-by-step guide on how to achieve this: 1. Define the object and the key you want to check:

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   const obj = { name: "John", age: 30 };
   const key = "name"; // Replace with the key you want to check

Replace{ name: "John", age: 30 } with your object, and"name" with the key you want to check. 2. Using thein operator:

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   const exists = key in obj;

Thein operator checks if the specified key exists as a property in the object. It returnstrue if the key exists andfalse otherwise. 3. Using thehasOwnProperty() method:

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   const exists = obj.hasOwnProperty(key);

ThehasOwnProperty() method is a built-in method of JavaScript objects. It checks if the object has a property with the specified key. It returnstrue if the key exists and is directly owned by the object, andfalse otherwise. 4. Using strict comparison withundefined:

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   const exists = obj[key] !== undefined;

This approach checks if accessing the key in the object returns a value that is notundefined. If the value is notundefined, it implies that the key exists in the object. Choose the method that best suits your needs and adjust the code as necessary to fit your specific use case. All these approaches are commonly used to check if a key exists in an object in JavaScript. Remember to consider edge cases, such as checking for keys that may haveundefined values or properties inherited from the object's prototype chain.

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