Sfdwhf

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I am having problem understanding the behavior of below code in JavaScript

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I am having problem understanding the behavior of below code in JavaScript

.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty{ height:90px;width:728px;box-sizing:border-box;
}

7

I was playing with below javascript code. Understanding of Object.defineProperty() and I am facing a strange issue with it. When I try to execute below code in the browser or in the VS code the output is not as expected whereas if I try to debug the code the output is correct

When I debug the code and evaluate the profile I can see the name & age property in the object
But at the time of output, it only shows the name property

//Code Snippet 

let profile = {

  name: 'Barry Allen',

}



// I added a new property in the profile object.

Object.defineProperty(profile, 'age', {

  value: 23,

  writable: true

})



console.log(profile)

console.log(profile.age)

Now expected output here should be

{name: "Barry Allen", age: 23}

23

but I get the output as.
Note that I am able to access the age property defined afterwards.
I am not sure why the console.log() is behaving this way.

{name: "Barry Allen"}

23 

javascript

share|improve this question

edited 32 mins ago

Eddie

20.3k51642

asked 33 mins ago

Ravi WRavi W

384

New contributor

Ravi W is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

add a comment | 

7

I was playing with below javascript code. Understanding of Object.defineProperty() and I am facing a strange issue with it. When I try to execute below code in the browser or in the VS code the output is not as expected whereas if I try to debug the code the output is correct

When I debug the code and evaluate the profile I can see the name & age property in the object
But at the time of output, it only shows the name property

//Code Snippet 

let profile = {

  name: 'Barry Allen',

}



// I added a new property in the profile object.

Object.defineProperty(profile, 'age', {

  value: 23,

  writable: true

})



console.log(profile)

console.log(profile.age)

Now expected output here should be

{name: "Barry Allen", age: 23}

23

but I get the output as.
Note that I am able to access the age property defined afterwards.
I am not sure why the console.log() is behaving this way.

{name: "Barry Allen"}

23 

javascript

share|improve this question

edited 32 mins ago

Eddie

20.3k51642

asked 33 mins ago

Ravi WRavi W

384

New contributor

Ravi W is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

add a comment | 

I was playing with below javascript code. Understanding of Object.defineProperty() and I am facing a strange issue with it. When I try to execute below code in the browser or in the VS code the output is not as expected whereas if I try to debug the code the output is correct

When I debug the code and evaluate the profile I can see the name & age property in the object
But at the time of output, it only shows the name property

//Code Snippet 

let profile = {

  name: 'Barry Allen',

}



// I added a new property in the profile object.

Object.defineProperty(profile, 'age', {

  value: 23,

  writable: true

})



console.log(profile)

console.log(profile.age)

Now expected output here should be

{name: "Barry Allen", age: 23}

23

but I get the output as.
Note that I am able to access the age property defined afterwards.
I am not sure why the console.log() is behaving this way.

{name: "Barry Allen"}

23 

javascript

share|improve this question

edited 32 mins ago

Eddie

20.3k51642

asked 33 mins ago

Ravi WRavi W

384

New contributor

Ravi W is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

//Code Snippet 

let profile = {

  name: 'Barry Allen',

}



// I added a new property in the profile object.

Object.defineProperty(profile, 'age', {

  value: 23,

  writable: true

})



console.log(profile)

console.log(profile.age)

{name: "Barry Allen", age: 23}

23

{name: "Barry Allen"}

23 

//Code Snippet 

let profile = {

  name: 'Barry Allen',

}



// I added a new property in the profile object.

Object.defineProperty(profile, 'age', {

  value: 23,

  writable: true

})



console.log(profile)

console.log(profile.age)

//Code Snippet 

let profile = {

  name: 'Barry Allen',

}



// I added a new property in the profile object.

Object.defineProperty(profile, 'age', {

  value: 23,

  writable: true

})



console.log(profile)

console.log(profile.age)

share|improve this question

edited 32 mins ago

Eddie

20.3k51642

asked 33 mins ago

Ravi WRavi W

384

New contributor

Ravi W is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

share|improve this question

edited 32 mins ago

Eddie

20.3k51642

asked 33 mins ago

Ravi WRavi W

384

New contributor

Ravi W is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

edited 32 mins ago

Eddie

20.3k51642

edited 32 mins ago

Eddie

20.3k51642

asked 33 mins ago

Ravi WRavi W

384

New contributor

Ravi W is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

asked 33 mins ago

Ravi WRavi W

384

3 Answers
3

active

oldest

votes

7

You should set enumerable to true. In Object.defineProperty its false by default. According to MDN.

enumerable

true if and only if this property shows up during enumeration of the properties on the corresponding object.
Defaults to false.

Non-enumerable means that property will not be shown in Object.keys() or for..in loop neither in console

let profile = {

    name: 'Barry Allen',

}



// I added a new property in the profile object.



Object.defineProperty(profile , 'age', {

    value: 23,

    writable: true,

    enumerable: true

})

console.log(profile)

console.log(profile.age)

Example: All the properties and methods on prototype object of built-in classes are non-enumerable. Thats is the reason you can call them from instance but they don't appear while iterating.

To get all properties(including non-enumerable)Object​.get​OwnProperty​Names()
.

share|improve this answer

edited 10 mins ago

answered 31 mins ago

Maheer AliMaheer Ali

11.5k826

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I didn't knew about this, but when I checked by running the local code in browser, it shows up perfectly (in spite of explicitly specifying enumerable to false).
  
  – randomSoul
  21 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @randomSoul I can't get what you mean.
  
  – Maheer Ali
  15 mins ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  See - pasteboard.co/IaOxMqB.png . I did not set enumerable to true for age, but still it is shown.
  
  – randomSoul
  10 mins ago
  
  
  

  
  
  
  

add a comment | 

6

By default, properties you define with defineProperty are not enumerable - this means that they will not show up when you console.log them, nor when you iterate over their Object.keys. (Similarly, the length property of an array does not get displayed, because it's non-enumerable.)

See MDN:

enumerable

true if and only if this property shows up during enumeration of the properties on the corresponding object.

Defaults to false.

Make it enumerable instead:

//Code Snippet 

let profile = {

  name: 'Barry Allen',

}



// I added a new property in the profile object.

Object.defineProperty(profile, 'age', {

  value: 23,

  writable: true,

  enumerable: true

})



console.log(profile)

console.log(profile.age)

share|improve this answer

answered 30 mins ago

CertainPerformanceCertainPerformance

101k166291

add a comment | 

2

Whenever you use".defineProperty" method of object. You should better define all the properties of the descriptor. Because if you don't define other property descriptor then it assumes default values for all of them which is false. So your console.log checks for all the enumerable : true properties and logs them.

//Code Snippet 

let profile = {

  name: 'Barry Allen',

}



// I added a new property in the profile object.

Object.defineProperty(profile, 'age', {

  value: 23,

  writable: true,

  enumerable : true,

  configurable : true

})



console.log(profile)

console.log(profile.age)

share|improve this answer

answered 28 mins ago

RK_15RK_15

5749

add a comment | 

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7

You should set enumerable to true. In Object.defineProperty its false by default. According to MDN.

enumerable

true if and only if this property shows up during enumeration of the properties on the corresponding object.
Defaults to false.

Non-enumerable means that property will not be shown in Object.keys() or for..in loop neither in console

let profile = {

    name: 'Barry Allen',

}



// I added a new property in the profile object.



Object.defineProperty(profile , 'age', {

    value: 23,

    writable: true,

    enumerable: true

})

console.log(profile)

console.log(profile.age)

Example: All the properties and methods on prototype object of built-in classes are non-enumerable. Thats is the reason you can call them from instance but they don't appear while iterating.

To get all properties(including non-enumerable)Object​.get​OwnProperty​Names()
.

share|improve this answer

edited 10 mins ago

answered 31 mins ago

Maheer AliMaheer Ali

11.5k826

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I didn't knew about this, but when I checked by running the local code in browser, it shows up perfectly (in spite of explicitly specifying enumerable to false).
  
  – randomSoul
  21 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @randomSoul I can't get what you mean.
  
  – Maheer Ali
  15 mins ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  See - pasteboard.co/IaOxMqB.png . I did not set enumerable to true for age, but still it is shown.
  
  – randomSoul
  10 mins ago
  
  
  

  
  
  
  

add a comment | 

7

You should set enumerable to true. In Object.defineProperty its false by default. According to MDN.

enumerable

true if and only if this property shows up during enumeration of the properties on the corresponding object.
Defaults to false.

Non-enumerable means that property will not be shown in Object.keys() or for..in loop neither in console

let profile = {

    name: 'Barry Allen',

}



// I added a new property in the profile object.



Object.defineProperty(profile , 'age', {

    value: 23,

    writable: true,

    enumerable: true

})

console.log(profile)

console.log(profile.age)

Example: All the properties and methods on prototype object of built-in classes are non-enumerable. Thats is the reason you can call them from instance but they don't appear while iterating.

To get all properties(including non-enumerable)Object​.get​OwnProperty​Names()
.

share|improve this answer

edited 10 mins ago

answered 31 mins ago

Maheer AliMaheer Ali

11.5k826

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I didn't knew about this, but when I checked by running the local code in browser, it shows up perfectly (in spite of explicitly specifying enumerable to false).
  
  – randomSoul
  21 mins ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @randomSoul I can't get what you mean.
  
  – Maheer Ali
  15 mins ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  See - pasteboard.co/IaOxMqB.png . I did not set enumerable to true for age, but still it is shown.
  
  – randomSoul
  10 mins ago
  
  
  

  
  
  
  

add a comment | 

You should set enumerable to true. In Object.defineProperty its false by default. According to MDN.

enumerable

true if and only if this property shows up during enumeration of the properties on the corresponding object.
Defaults to false.

Non-enumerable means that property will not be shown in Object.keys() or for..in loop neither in console

let profile = {

    name: 'Barry Allen',

}



// I added a new property in the profile object.



Object.defineProperty(profile , 'age', {

    value: 23,

    writable: true,

    enumerable: true

})

console.log(profile)

console.log(profile.age)

Example: All the properties and methods on prototype object of built-in classes are non-enumerable. Thats is the reason you can call them from instance but they don't appear while iterating.

To get all properties(including non-enumerable)Object​.get​OwnProperty​Names()
.

share|improve this answer

edited 10 mins ago

answered 31 mins ago

Maheer AliMaheer Ali

11.5k826

let profile = {

    name: 'Barry Allen',

}



// I added a new property in the profile object.



Object.defineProperty(profile , 'age', {

    value: 23,

    writable: true,

    enumerable: true

})

console.log(profile)

console.log(profile.age)

let profile = {

    name: 'Barry Allen',

}



// I added a new property in the profile object.



Object.defineProperty(profile , 'age', {

    value: 23,

    writable: true,

    enumerable: true

})

console.log(profile)

console.log(profile.age)

let profile = {

    name: 'Barry Allen',

}



// I added a new property in the profile object.



Object.defineProperty(profile , 'age', {

    value: 23,

    writable: true,

    enumerable: true

})

console.log(profile)

console.log(profile.age)

share|improve this answer

edited 10 mins ago

answered 31 mins ago

Maheer AliMaheer Ali

11.5k826

answered 31 mins ago

Maheer AliMaheer Ali

11.5k826

answered 31 mins ago

Maheer AliMaheer Ali

11.5k826

6

By default, properties you define with defineProperty are not enumerable - this means that they will not show up when you console.log them, nor when you iterate over their Object.keys. (Similarly, the length property of an array does not get displayed, because it's non-enumerable.)

See MDN:

enumerable

true if and only if this property shows up during enumeration of the properties on the corresponding object.

Defaults to false.

Make it enumerable instead:

//Code Snippet 

let profile = {

  name: 'Barry Allen',

}



// I added a new property in the profile object.

Object.defineProperty(profile, 'age', {

  value: 23,

  writable: true,

  enumerable: true

})



console.log(profile)

console.log(profile.age)

share|improve this answer

answered 30 mins ago

CertainPerformanceCertainPerformance

101k166291

add a comment | 

6

By default, properties you define with defineProperty are not enumerable - this means that they will not show up when you console.log them, nor when you iterate over their Object.keys. (Similarly, the length property of an array does not get displayed, because it's non-enumerable.)

See MDN:

enumerable

true if and only if this property shows up during enumeration of the properties on the corresponding object.

Defaults to false.

Make it enumerable instead:

//Code Snippet 

let profile = {

  name: 'Barry Allen',

}



// I added a new property in the profile object.

Object.defineProperty(profile, 'age', {

  value: 23,

  writable: true,

  enumerable: true

})



console.log(profile)

console.log(profile.age)

share|improve this answer

answered 30 mins ago

CertainPerformanceCertainPerformance

101k166291

add a comment | 

By default, properties you define with defineProperty are not enumerable - this means that they will not show up when you console.log them, nor when you iterate over their Object.keys. (Similarly, the length property of an array does not get displayed, because it's non-enumerable.)

See MDN:

enumerable

true if and only if this property shows up during enumeration of the properties on the corresponding object.

Defaults to false.

Make it enumerable instead:

//Code Snippet 

let profile = {

  name: 'Barry Allen',

}



// I added a new property in the profile object.

Object.defineProperty(profile, 'age', {

  value: 23,

  writable: true,

  enumerable: true

})



console.log(profile)

console.log(profile.age)

share|improve this answer

answered 30 mins ago

CertainPerformanceCertainPerformance

101k166291

//Code Snippet 

let profile = {

  name: 'Barry Allen',

}



// I added a new property in the profile object.

Object.defineProperty(profile, 'age', {

  value: 23,

  writable: true,

  enumerable: true

})



console.log(profile)

console.log(profile.age)

//Code Snippet 

let profile = {

  name: 'Barry Allen',

}



// I added a new property in the profile object.

Object.defineProperty(profile, 'age', {

  value: 23,

  writable: true,

  enumerable: true

})



console.log(profile)

console.log(profile.age)

//Code Snippet 

let profile = {

  name: 'Barry Allen',

}



// I added a new property in the profile object.

Object.defineProperty(profile, 'age', {

  value: 23,

  writable: true,

  enumerable: true

})



console.log(profile)

console.log(profile.age)

share|improve this answer

answered 30 mins ago

CertainPerformanceCertainPerformance

101k166291

answered 30 mins ago

CertainPerformanceCertainPerformance

101k166291

answered 30 mins ago

CertainPerformanceCertainPerformance

101k166291

2

Whenever you use".defineProperty" method of object. You should better define all the properties of the descriptor. Because if you don't define other property descriptor then it assumes default values for all of them which is false. So your console.log checks for all the enumerable : true properties and logs them.

//Code Snippet 

let profile = {

  name: 'Barry Allen',

}



// I added a new property in the profile object.

Object.defineProperty(profile, 'age', {

  value: 23,

  writable: true,

  enumerable : true,

  configurable : true

})



console.log(profile)

console.log(profile.age)

share|improve this answer

answered 28 mins ago

RK_15RK_15

5749

add a comment | 

2

Whenever you use".defineProperty" method of object. You should better define all the properties of the descriptor. Because if you don't define other property descriptor then it assumes default values for all of them which is false. So your console.log checks for all the enumerable : true properties and logs them.

//Code Snippet 

let profile = {

  name: 'Barry Allen',

}



// I added a new property in the profile object.

Object.defineProperty(profile, 'age', {

  value: 23,

  writable: true,

  enumerable : true,

  configurable : true

})



console.log(profile)

console.log(profile.age)

share|improve this answer

answered 28 mins ago

RK_15RK_15

5749

add a comment | 

Whenever you use".defineProperty" method of object. You should better define all the properties of the descriptor. Because if you don't define other property descriptor then it assumes default values for all of them which is false. So your console.log checks for all the enumerable : true properties and logs them.

//Code Snippet 

let profile = {

  name: 'Barry Allen',

}



// I added a new property in the profile object.

Object.defineProperty(profile, 'age', {

  value: 23,

  writable: true,

  enumerable : true,

  configurable : true

})



console.log(profile)

console.log(profile.age)

share|improve this answer

answered 28 mins ago

RK_15RK_15

5749

//Code Snippet 

let profile = {

  name: 'Barry Allen',

}



// I added a new property in the profile object.

Object.defineProperty(profile, 'age', {

  value: 23,

  writable: true,

  enumerable : true,

  configurable : true

})



console.log(profile)

console.log(profile.age)

share|improve this answer

answered 28 mins ago

RK_15RK_15

5749

answered 28 mins ago

RK_15RK_15

5749

answered 28 mins ago

RK_15RK_15

5749