I am so confused about Object in JavaScript












6















I am a newbie to JavaScript, but I am familiar with Python. I am trying to figure out the differences between the Dictionary in Python and the Object in JS.



As far as I know, the key in a dictionary in Python needs to be defined in advance, but it could be undefined in an object in JS. However, I am confused about those cases:



var n = 'name';

var n2 = n;

var person = {n: 'mike'};



person.n    # 'mike'

person['n'] # 'mike'

person[n2]  # undefined

person.n2   # undefined

person['name']  # undefined

person.'name'  # undefined


I am so confused that why those three variables n, n2 and name are not equal, because compared with that in Python:



n = 'name'

n2 = n

person = {n:'mike'}



person[n]  # 'mike'

person[n2] # 'mike'

person['name'] # 'mike'


I guess that might due to the fact that in Python, n and n2 both point to the unique string object 'name', so they are the same. But could someone explain the mechanism behind in JS to me?






javascript python object







share|improve this question



























    6















    I am a newbie to JavaScript, but I am familiar with Python. I am trying to figure out the differences between the Dictionary in Python and the Object in JS.



    As far as I know, the key in a dictionary in Python needs to be defined in advance, but it could be undefined in an object in JS. However, I am confused about those cases:



    var n = 'name';
    
var n2 = n;
    
var person = {n: 'mike'};
    

    
person.n    # 'mike'
    
person['n'] # 'mike'
    
person[n2]  # undefined
    
person.n2   # undefined
    
person['name']  # undefined
    
person.'name'  # undefined


    I am so confused that why those three variables n, n2 and name are not equal, because compared with that in Python:



    n = 'name'
    
n2 = n
    
person = {n:'mike'}
    

    
person[n]  # 'mike'
    
person[n2] # 'mike'
    
person['name'] # 'mike'


    I guess that might due to the fact that in Python, n and n2 both point to the unique string object 'name', so they are the same. But could someone explain the mechanism behind in JS to me?






    javascript python object







    share|improve this question

























      6












      6








      6








      I am a newbie to JavaScript, but I am familiar with Python. I am trying to figure out the differences between the Dictionary in Python and the Object in JS.



      As far as I know, the key in a dictionary in Python needs to be defined in advance, but it could be undefined in an object in JS. However, I am confused about those cases:



      var n = 'name';
      
var n2 = n;
      
var person = {n: 'mike'};
      

      
person.n    # 'mike'
      
person['n'] # 'mike'
      
person[n2]  # undefined
      
person.n2   # undefined
      
person['name']  # undefined
      
person.'name'  # undefined


      I am so confused that why those three variables n, n2 and name are not equal, because compared with that in Python:



      n = 'name'
      
n2 = n
      
person = {n:'mike'}
      

      
person[n]  # 'mike'
      
person[n2] # 'mike'
      
person['name'] # 'mike'


      I guess that might due to the fact that in Python, n and n2 both point to the unique string object 'name', so they are the same. But could someone explain the mechanism behind in JS to me?






      javascript python object







      share|improve this question














      I am a newbie to JavaScript, but I am familiar with Python. I am trying to figure out the differences between the Dictionary in Python and the Object in JS.



      As far as I know, the key in a dictionary in Python needs to be defined in advance, but it could be undefined in an object in JS. However, I am confused about those cases:



      var n = 'name';
      
var n2 = n;
      
var person = {n: 'mike'};
      

      
person.n    # 'mike'
      
person['n'] # 'mike'
      
person[n2]  # undefined
      
person.n2   # undefined
      
person['name']  # undefined
      
person.'name'  # undefined


      I am so confused that why those three variables n, n2 and name are not equal, because compared with that in Python:



      n = 'name'
      
n2 = n
      
person = {n:'mike'}
      

      
person[n]  # 'mike'
      
person[n2] # 'mike'
      
person['name'] # 'mike'


      I guess that might due to the fact that in Python, n and n2 both point to the unique string object 'name', so they are the same. But could someone explain the mechanism behind in JS to me?






      javascript python object




      javascript python object






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked Nov 24 '18 at 3:00









      AuroraAurora

      1078




      1078
























          1 Answer
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          active

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          6














          When you assign like:



          var person = {n: 'mike'};


          The n is not referencing to the variable but it's own property. If you need to reference the variable you will need to use bracket notation like:



          var person = {[n]: 'mike'};


          For more information about bracket notation, see computed property.



          In JavaScript, the use of quote for property is same without using quote:



          var person = {n: 'mike'};
          
var person = {'n': 'mike'}; // same as above


          But if you define property like giving space:



          var person = {my property: 'mike'}; // invalid


          In this case, you must need to use the quote:



          var person = {'my property': 'mike'};





          share|improve this answer





















          • 2





            I guess in Python the equivalent of Javascript's {n: "mike"} is {"n": "mike"}

            – Thilo
            Nov 24 '18 at 3:04











          Your Answer






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          1 Answer
          1






          active

          oldest

          votes








          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          6














          When you assign like:



          var person = {n: 'mike'};


          The n is not referencing to the variable but it's own property. If you need to reference the variable you will need to use bracket notation like:



          var person = {[n]: 'mike'};


          For more information about bracket notation, see computed property.



          In JavaScript, the use of quote for property is same without using quote:



          var person = {n: 'mike'};
          
var person = {'n': 'mike'}; // same as above


          But if you define property like giving space:



          var person = {my property: 'mike'}; // invalid


          In this case, you must need to use the quote:



          var person = {'my property': 'mike'};





          share|improve this answer





















          • 2





            I guess in Python the equivalent of Javascript's {n: "mike"} is {"n": "mike"}

            – Thilo
            Nov 24 '18 at 3:04
















          6














          When you assign like:



          var person = {n: 'mike'};


          The n is not referencing to the variable but it's own property. If you need to reference the variable you will need to use bracket notation like:



          var person = {[n]: 'mike'};


          For more information about bracket notation, see computed property.



          In JavaScript, the use of quote for property is same without using quote:



          var person = {n: 'mike'};
          
var person = {'n': 'mike'}; // same as above


          But if you define property like giving space:



          var person = {my property: 'mike'}; // invalid


          In this case, you must need to use the quote:



          var person = {'my property': 'mike'};





          share|improve this answer





















          • 2





            I guess in Python the equivalent of Javascript's {n: "mike"} is {"n": "mike"}

            – Thilo
            Nov 24 '18 at 3:04














          6












          6








          6







          When you assign like:



          var person = {n: 'mike'};


          The n is not referencing to the variable but it's own property. If you need to reference the variable you will need to use bracket notation like:



          var person = {[n]: 'mike'};


          For more information about bracket notation, see computed property.



          In JavaScript, the use of quote for property is same without using quote:



          var person = {n: 'mike'};
          
var person = {'n': 'mike'}; // same as above


          But if you define property like giving space:



          var person = {my property: 'mike'}; // invalid


          In this case, you must need to use the quote:



          var person = {'my property': 'mike'};





          share|improve this answer















          When you assign like:



          var person = {n: 'mike'};


          The n is not referencing to the variable but it's own property. If you need to reference the variable you will need to use bracket notation like:



          var person = {[n]: 'mike'};


          For more information about bracket notation, see computed property.



          In JavaScript, the use of quote for property is same without using quote:



          var person = {n: 'mike'};
          
var person = {'n': 'mike'}; // same as above


          But if you define property like giving space:



          var person = {my property: 'mike'}; // invalid


          In this case, you must need to use the quote:



          var person = {'my property': 'mike'};






          share|improve this answer














          share|improve this answer



          share|improve this answer








          edited Nov 24 '18 at 3:09

























          answered Nov 24 '18 at 3:03









          Bhojendra RauniyarBhojendra Rauniyar

          51.3k2079127




          51.3k2079127








          • 2





            I guess in Python the equivalent of Javascript's {n: "mike"} is {"n": "mike"}

            – Thilo
            Nov 24 '18 at 3:04














          • 2





            I guess in Python the equivalent of Javascript's {n: "mike"} is {"n": "mike"}

            – Thilo
            Nov 24 '18 at 3:04








          2




          2





          I guess in Python the equivalent of Javascript's {n: "mike"} is {"n": "mike"}

          – Thilo
          Nov 24 '18 at 3:04





          I guess in Python the equivalent of Javascript's {n: "mike"} is {"n": "mike"}

          – Thilo
          Nov 24 '18 at 3:04




















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