[TIL] 20201201 JavaScript Object Literals

Objects

• Collections of properties
• Property is a key-value pair
• Rather than accessing data using an index, we use custom keys.

 

 

Creating Object Literals

• Syntax
  • const obj = {key : value}
• Example

const human = {
    firstName : 'Jiwan',
    lastName : 'Kim'
}

 

 

Accessing Data Out of Objects

• Syntax
  • obj["key"]
  • obj.key
  • Examples
    • human["firstName"] //Jiwan
    • human.lastName //Kim
• Keys
  • All keys are converted to strings, except for symbols.
  • obj[variableName] is also possible.
  • Example

const years = {1995: 'pig', 1997: 'cow'}
let birthYear = 1995;

years.birthYear  //undefined
years[birthYear]  //'pig'
years["birthYear"]  //undefined

 

 

Modifying Objects

• Using const with objects
  • Just like arrays, using const, the reference of the object stays the same. Hence, using const instead of let is safer.
• Modifying objects
  • Access to the property using key, and define the value. (Do the same when assigning a new property)
  • Example

const grades = {rob='A', dani='A+', emily='B'}
grades.emily = 'B+'; //modified
grades.hannah = 'A-'; //added

 

 

Nesting Arrays & Objects

• Arrays + Objects
  • It's possible to nest arrays and objects. Very Useful in real life.

 

 

 

 

* This post is a summary of Udemy Course "The Web Developer Bootcamp" by Colt Steele.