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5.1: detecting properties, and changing attributes - Coggle Diagram

- - - - is in the object
      - or its prototype chain
  - - - in the prototype
    - - if the specified property
        
        is in the object
        
        as its own property
        
        NOT inherited
  - - - > Name: firstName, value: Steven > Name: lastName, value: Hancock > Name: email, value: shancock@allthingsjavascript.com > Name: type, value: admin > Name: active, value: true > Name: address, value: [object Object]
      - only shows properties in the object
        
        why:question:
        
        because it only iterates over properties that are iterable
        
        all properties have attributes
        
        one of these
        
        indicates that the property is enumerable
        
        and can be iterated over in a for...in loop
        
        so, for an object property
        
        outputs
        
        1 more item...
        
        > person1.propertyIsEnumerable('firstName')
        
        but for a prototype property
        
        outputs
        
        1 more item...
        
        > person1.propertyIsEnumerable('toString')
        
        :!:not in the prototype
  - - - an array
      - > (6) ['firstName', 'lastName', 'email', 'type', 'active', 'address']
- - - - > true
    - - using
        
        > Object.defineProperty(obj,'type', {enumerable: false})
      - and now
        
        > obj.propertyIsEnumerable('type')
        
        outputs
        
        > false
      - type is no longer discoverable by
        
        Object.keys
        
        for...in loop
  - - - allows you to
        
        change the attributes of a property #
        
        delete the property
    - - > Object.defineProperty(obj,'type', {configurable: false})
      - can't delete
        
        > delete obj.type
        
        returns false
        
        and fails to delete type
        
        in strict mode
        
        will generate an error