JavaScript Object Properties and Methods

1. for...in Loop

   • Description: Iterates over all enumerable properties of an object.

   • Use: Useful for iterating through the properties of an object.

   • Example:

     for (const key in dog) {
       console.log(key, dog[key]);
     }
     // Output: name Max, age 6, color black
     
     

2. Object.keys()

   • Description: Returns an array of a given object's own enumerable property names.

   • Use: Useful for getting all the keys of an object.

   • Example:

     let keys = Object.keys(dog);
     console.log(keys); // Output: [ 'name', 'age', 'color' ]
     
     

3. for...of Loop

   • Description: Iterates over the values of an iterable object.

   • Use: Useful for iterating through arrays or other iterable objects.

   • Example:

     for (const key of keys) {
       console.log(key, dog[key]);
     }
     // Output: name Max, age 6, color black
     
     

4. Object.values()

   • Description: Returns an array of a given object's own enumerable property values.

   • Use: Useful for getting all the values of an object.

   • Example:

     let values = Object.values(dog);
     console.log(values); // Output: [ 'Max', 6, 'black' ]
     
     

5. Object.entries()

   • Description: Returns an array of a given object's own enumerable property [key, value] pairs.

   • Use: Useful for getting both keys and values of an object.

   • Example:

     let entries = Object.entries(dog);
     console.log(entries); // Output: [ [ 'name', 'Max' ], [ 'age', 6 ], [ 'color', 'black' ] ]
     
     

6. Object.getOwnPropertyDescriptors()

   • Description: Returns all own property descriptors of an object.

   • Use: Useful for getting detailed information about an object's properties.

   • Example:

     let descriptors = Object.getOwnPropertyDescriptors(dog);
     console.log(descriptors);
     // Output: { name: { value: 'Max', writable: true, enumerable: true, configurable: true }, age: { value: 6, writable: true, enumerable: true, configurable: true }, color: { value: 'black', writable: true, enumerable: true, configurable: true } }
     
     

7. Object.getOwnPropertySymbols()

   • Description: Returns an array of all symbol properties found directly on a given object.

   • Use: Useful for working with symbol properties of an object.

   • Example:

     let symbols = Object.getOwnPropertySymbols(dog);
     console.log(symbols); // Output: []
     
     

8. Object.freeze()

   • Description: Freezes an object, preventing new properties from being added, existing properties from being removed, and existing properties from being changed.

   • Use: Useful for making an object immutable.

   • Example:

     Object.freeze(dog);
     dog.name = 'Maxwell';
     console.log(dog); // Output: { name: 'Max', age: 6, color: 'black' }
     
     

9. Object.seal()

   • Description: Seals an object, preventing new properties from being added or existing properties from being removed. Existing properties can still be modified.

   • Use: Useful for partially making an object immutable.

   • Example:

     Object.seal(dog);
     dog.breed = 'German Shepherd';
     console.log(dog); // Output: { name: 'Max', age: 6, color: 'black' }
     
     

10. Object.preventExtensions()

    • Description: Prevents new properties from being added to an object.

    • Use: Useful for ensuring no new properties can be added to an object.

    • Example:

      Object.preventExtensions(dog);
      dog.breed = 'German Shepherd';
      console.log(dog); // Output: { name: 'Max', age: 6, color: 'black' }
      
      

11. Object.isFrozen()

    • Description: Determines if an object is frozen.

    • Use: Useful for checking if an object is immutable.

    • Example:

      let isFrozen = Object.isFrozen(dog);
      console.log(isFrozen); // Output: true
      
      

12. Object.isSealed()

    • Description: Determines if an object is sealed.

    • Use: Useful for checking if an object is partially immutable.

    • Example:

      let isSealed = Object.isSealed(dog);
      console.log(isSealed); // Output: true
      
      

13. Object.isExtensible()

    • Description: Determines if an object is extensible (i.e., if new properties can be added to it).

    • Use: Useful for checking if new properties can be added to an object.

    • Example:

      let isExtensible = Object.isExtensible(dog);
      console.log(isExtensible); // Output: false
      
      

14. Object.assign()

    • Description: Copies all enumerable own properties from one or more source objects to a target object.

    • Use: Useful for merging objects or cloning an object.

    • Example:

      let assign = Object.assign({}, dog);
      console.log(assign); // Output: { name: 'Max', age: 6, color: 'black' }
      
      

15. Object.defineProperty()

    • Description: Defines a new property directly on an object or modifies an existing property on an object.

    • Use: Useful for adding or modifying properties with specific descriptors.

    • Example:

      Object.defineProperty(dog, 'breed', {
        value: 'German Shepherd',
        writable: true,
        enumerable: true,
        configurable: true
      });
      console.log(dog); // Output: { name: 'Max', age: 6, color: 'black', breed: 'German Shepherd' }
      
      

16. Object.defineProperties()

    • Description: Defines new or modifies existing properties directly on an object, returning the object.

    • Use: Useful for defining multiple properties with specific descriptors at once.

    • Example:

      Object.defineProperties(dog, {
        breed: {
          value: 'German Shepherd',
          writable: true,
          enumerable: true,
          configurable: true
        },
        weight: {
          value: '100 lbs',
          writable: true,
          enumerable: true,
          configurable: true
        }
      });
      console.log(dog); // Output: { name: 'Max', age: 6, color: 'black', breed: 'German Shepherd', weight: '100 lbs' }