JS objects

• objects.      
  • objects are collections of properties
  • properties are a key-value pair
  • use costom keys to access data rather than using an index.
• key-value pairs:   property = key + value
  • username: "smart_rich"
  • upvotes: 7
  • text: "nice vlog!"
• dictionay property. (一一对应)
• all types welcome.(可以多种类型混合存储)
• valid keys, all keys are converted to strings * (except for symbols)
• access data out of objects

  • const papers = {
        red : "shdkshdks"
        blue: "jshdjshdd"
        yellow: "sdhjshd"
    }
    
    papers.red
    papers['blue']
    
    let color = 'red';
    papers[color] // "shdkshdks"

     

• updating & adding properties

• // To make an object literal:
  const dog = {
      name: "Rusty",
      breed: "unknown",
      isAlive: false,
      age: 7
  }
  // All keys will be turned into strings!
  
  // To retrieve a value:
  dog.age; //7
  dog["age"]; //7
  
  //updating values
  dog.breed = "mutt";
  dog["age"] = 8;
  
  //addin a new property
  dog["isHappy"] = true;

  Arrays + Objects

shoppingCart[2].product = "Fire Stick"