Manipulating Object Properties
When working with JavaScript objects, you often need to add, update, or remove properties to keep your data accurate and up-to-date. Understanding how to manipulate object properties is essential for dynamic applications, where the structure of your data can change during execution. You can add new properties to an object simply by assigning a value to a new property name, update existing properties by assigning a new value to an existing property, and remove properties with the delete operator.
12345678910111213// Adding and updating properties const user = { name: "Alice", age: 28 }; // Add a new property user.email = "alice@example.com"; // Update an existing property user.age = 29; console.log(JSON.stringify(user));
1234567891011// Deleting properties const product = { id: 101, name: "Book", price: 12.99 }; // Remove the price property delete product.price; console.log(JSON.stringify(product));
After manipulating properties, you may want to check whether a property exists on an object. JavaScript provides a couple of ways to do this: the in operator and the hasOwnProperty method.
- The
inoperator checks if a property exists anywhere in the object's prototype chain; - The
hasOwnPropertychecks only for properties directly on the object itself. For example, after adding and deleting properties as shown above, you can use these checks to confirm the presence or absence of specific properties.
123456789101112131415const car = { make: "Toyota", model: "Corolla" }; // Add a new property car.year = 2018; // Check property existence with 'in' console.log("year" in car); // true console.log("color" in car); // false // Check property existence with hasOwnProperty console.log(car.hasOwnProperty("model")); // true console.log(car.hasOwnProperty("toString")); // false (inherited from prototype)
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When working with JavaScript objects, you often need to add, update, or remove properties to keep your data accurate and up-to-date. Understanding how to manipulate object properties is essential for dynamic applications, where the structure of your data can change during execution. You can add new properties to an object simply by assigning a value to a new property name, update existing properties by assigning a new value to an existing property, and remove properties with the delete operator.
12345678910111213// Adding and updating properties const user = { name: "Alice", age: 28 }; // Add a new property user.email = "alice@example.com"; // Update an existing property user.age = 29; console.log(JSON.stringify(user));
1234567891011// Deleting properties const product = { id: 101, name: "Book", price: 12.99 }; // Remove the price property delete product.price; console.log(JSON.stringify(product));
After manipulating properties, you may want to check whether a property exists on an object. JavaScript provides a couple of ways to do this: the in operator and the hasOwnProperty method.
- The
inoperator checks if a property exists anywhere in the object's prototype chain; - The
hasOwnPropertychecks only for properties directly on the object itself. For example, after adding and deleting properties as shown above, you can use these checks to confirm the presence or absence of specific properties.
123456789101112131415const car = { make: "Toyota", model: "Corolla" }; // Add a new property car.year = 2018; // Check property existence with 'in' console.log("year" in car); // true console.log("color" in car); // false // Check property existence with hasOwnProperty console.log(car.hasOwnProperty("model")); // true console.log(car.hasOwnProperty("toString")); // false (inherited from prototype)
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