JavaScript Object Functions Cheat Sheet Part 2

 JavaScript Object Functions Part 1

Object.freeze()

Object.freeze() freezes an object, which then can no longer be changed.

Syntax 

  Object.freeze(obj)

Example

  

  const obj = {

    a: 1

  }

  Object.freeze(obj)

  obj.prop = 2 // error in strict mode

  console.log(obj.prop) // 1

Object.fromEntries()

Object.fromEntries() transforms a list of key-value pairs into an object.

Syntax

 

    Object.fromEntries(iterable)

Example

  

  Object.fromEntries([

    ['a', 1],

    ['b', 2]

  ]) // { a: 1, b: 2 }

Object.getOwnPropertyDescriptor()

Object,getOwnPropertyDescruotor() returns a property descriptor for an own property.

Syntax

  

    Object.getOwnPropertyDescriptor(obj, prop)

Example

  

  const obj = {

    a: 1

  }

  Object.getOwnPropertyDescriptor(obj, 'a')

  // { value: 1, writable: true, enumerable: 

  //true, configurable: true }

Object.getOwnPropertyNames()

Object.getOwnPropertyNames() returns array of all properties

Syntax

  

    Object.getOwnPropertyNames(obj)

Example

 

 Object.getOwnPropertyNames({

    a: 1,

    b: 2

  })

  // [ "a", "b" ]

Object.getOwnPropertySymbols()

array of all symbol properties

Syntax

  Object.getOwnPropertySymbols(obj)

  

Example

  const obj = {

    a: 1

  }

  const b = Symbol('b')

  obj[b] = 'someSymbol'

  // obj = { a: 1, Symbol(b): "symbol" }

  Object.getOwnPropertySymbols(obj)

  // [ Symbol(b) ]

  

Object.getPrototypeOf()

Object.getPrototypeOf() returns the prototype

Syntax

  Object.getPrototypeOf(obj)

Example

  const proto = {

    a: 1

  }

  const obj = Object.create(proto)

  obj.b = 2 // obj = { b: 2 }

  Object.getPrototypeOf(obj)

  // { a: 1 }

  

Object.is()

Object.is() determines whether two values are the same value.

Syntax

  Object.is(value1, value2)

Example

  

const objA = {

    a: 1

  }

  const objB = {

    a: 1

  }

  Object.is(objA, objA) // true

  Object.is(objA, objB) // false

  Object.is('a', 'a') // true

  

Javascript Cheat Sheet Object function part 1

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