How to insert an item into an empty array at a specific index?





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1















I want to insert a item to specified index of an empty Array. I saw there is Array.prototype.splice method. However, if I use splice on empty Array, it just add item to end off Array as shown below.



var a = ;

a.splice(3,0,"item-3");

console.log(a); //returns ['item-3']


What I want to accomplish is to have array as given below. 



console.log(a); //returns [,,,'item-3']

or

console.log(a); //returns [undefined,undefined,undefined,'item-3']


Thanks for your help.



Edit: I saw the question on How to insert an item into an array at a specific index? but, it did not explain how to insert to specified index of empty array.






javascript arrays







share|improve this question

























  • Do you mean a[3] = "item-3"? This is not a good idea to do this though.

    – Yeldar Kurmangaliyev
    Jan 4 at 12:21













  • Why it is not good idea to do ? I mean of course there will be undefined items but other than that is there any bad side ? @YeldarKurmangaliyev

    – ysnfrk
    Jan 4 at 12:33













  • Possible duplicate of How to insert an item into an array at a specific index?

    – Shahnewaz
    Jan 4 at 12:37






  • 2





    @ysnfrk Because this is not how an array is supposed to be used. If you do var a = ; a[100000] = true;, then a.length will be 100001. Also, most of algorithms rely on this length, which can cause many problems. Just use object set if you need key-value association array.

    – Yeldar Kurmangaliyev
    Jan 4 at 14:29


















1















I want to insert a item to specified index of an empty Array. I saw there is Array.prototype.splice method. However, if I use splice on empty Array, it just add item to end off Array as shown below.



var a = ;

a.splice(3,0,"item-3");

console.log(a); //returns ['item-3']


What I want to accomplish is to have array as given below. 



console.log(a); //returns [,,,'item-3']

or

console.log(a); //returns [undefined,undefined,undefined,'item-3']


Thanks for your help.



Edit: I saw the question on How to insert an item into an array at a specific index? but, it did not explain how to insert to specified index of empty array.






javascript arrays







share|improve this question

























  • Do you mean a[3] = "item-3"? This is not a good idea to do this though.

    – Yeldar Kurmangaliyev
    Jan 4 at 12:21













  • Why it is not good idea to do ? I mean of course there will be undefined items but other than that is there any bad side ? @YeldarKurmangaliyev

    – ysnfrk
    Jan 4 at 12:33













  • Possible duplicate of How to insert an item into an array at a specific index?

    – Shahnewaz
    Jan 4 at 12:37






  • 2





    @ysnfrk Because this is not how an array is supposed to be used. If you do var a = ; a[100000] = true;, then a.length will be 100001. Also, most of algorithms rely on this length, which can cause many problems. Just use object set if you need key-value association array.

    – Yeldar Kurmangaliyev
    Jan 4 at 14:29














1












1








1








I want to insert a item to specified index of an empty Array. I saw there is Array.prototype.splice method. However, if I use splice on empty Array, it just add item to end off Array as shown below.



var a = ;

a.splice(3,0,"item-3");

console.log(a); //returns ['item-3']


What I want to accomplish is to have array as given below. 



console.log(a); //returns [,,,'item-3']

or

console.log(a); //returns [undefined,undefined,undefined,'item-3']


Thanks for your help.



Edit: I saw the question on How to insert an item into an array at a specific index? but, it did not explain how to insert to specified index of empty array.






javascript arrays







share|improve this question
















I want to insert a item to specified index of an empty Array. I saw there is Array.prototype.splice method. However, if I use splice on empty Array, it just add item to end off Array as shown below.



var a = ;

a.splice(3,0,"item-3");

console.log(a); //returns ['item-3']


What I want to accomplish is to have array as given below. 



console.log(a); //returns [,,,'item-3']

or

console.log(a); //returns [undefined,undefined,undefined,'item-3']


Thanks for your help.



Edit: I saw the question on How to insert an item into an array at a specific index? but, it did not explain how to insert to specified index of empty array.






javascript arrays




javascript arrays






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited Jan 4 at 12:43







ysnfrk

















asked Jan 4 at 12:20









ysnfrkysnfrk

189




189













  • Do you mean a[3] = "item-3"? This is not a good idea to do this though.

    – Yeldar Kurmangaliyev
    Jan 4 at 12:21













  • Why it is not good idea to do ? I mean of course there will be undefined items but other than that is there any bad side ? @YeldarKurmangaliyev

    – ysnfrk
    Jan 4 at 12:33













  • Possible duplicate of How to insert an item into an array at a specific index?

    – Shahnewaz
    Jan 4 at 12:37






  • 2





    @ysnfrk Because this is not how an array is supposed to be used. If you do var a = ; a[100000] = true;, then a.length will be 100001. Also, most of algorithms rely on this length, which can cause many problems. Just use object set if you need key-value association array.

    – Yeldar Kurmangaliyev
    Jan 4 at 14:29



















  • Do you mean a[3] = "item-3"? This is not a good idea to do this though.

    – Yeldar Kurmangaliyev
    Jan 4 at 12:21













  • Why it is not good idea to do ? I mean of course there will be undefined items but other than that is there any bad side ? @YeldarKurmangaliyev

    – ysnfrk
    Jan 4 at 12:33













  • Possible duplicate of How to insert an item into an array at a specific index?

    – Shahnewaz
    Jan 4 at 12:37






  • 2





    @ysnfrk Because this is not how an array is supposed to be used. If you do var a = ; a[100000] = true;, then a.length will be 100001. Also, most of algorithms rely on this length, which can cause many problems. Just use object set if you need key-value association array.

    – Yeldar Kurmangaliyev
    Jan 4 at 14:29

















Do you mean a[3] = "item-3"? This is not a good idea to do this though.

– Yeldar Kurmangaliyev
Jan 4 at 12:21







Do you mean a[3] = "item-3"? This is not a good idea to do this though.

– Yeldar Kurmangaliyev
Jan 4 at 12:21















Why it is not good idea to do ? I mean of course there will be undefined items but other than that is there any bad side ? @YeldarKurmangaliyev

– ysnfrk
Jan 4 at 12:33







Why it is not good idea to do ? I mean of course there will be undefined items but other than that is there any bad side ? @YeldarKurmangaliyev

– ysnfrk
Jan 4 at 12:33















Possible duplicate of How to insert an item into an array at a specific index?

– Shahnewaz
Jan 4 at 12:37





Possible duplicate of How to insert an item into an array at a specific index?

– Shahnewaz
Jan 4 at 12:37




2




2





@ysnfrk Because this is not how an array is supposed to be used. If you do var a = ; a[100000] = true;, then a.length will be 100001. Also, most of algorithms rely on this length, which can cause many problems. Just use object set if you need key-value association array.

– Yeldar Kurmangaliyev
Jan 4 at 14:29





@ysnfrk Because this is not how an array is supposed to be used. If you do var a = ; a[100000] = true;, then a.length will be 100001. Also, most of algorithms rely on this length, which can cause many problems. Just use object set if you need key-value association array.

– Yeldar Kurmangaliyev
Jan 4 at 14:29












2 Answers
2






active

oldest

votes


















4














Just use the index and do the assignment directly:






var a = ;



a[3] = "item-3";



console.log(a);








share|improve this answer





















  • 2





    (As always: Hope my edit is helpful, but if not, please revert it.)

    – T.J. Crowder
    Jan 4 at 12:23



















0














Coming in for the ES6 solution:



[...Array(3), 'item-3']

// [undefined, undefined, undefined, "item-3"]





share|improve this answer
























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    2 Answers
    2






    active

    oldest

    votes








    2 Answers
    2






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes









    4














    Just use the index and do the assignment directly:






    var a = ;
    

    
a[3] = "item-3";
    

    
console.log(a);








    share|improve this answer





















    • 2





      (As always: Hope my edit is helpful, but if not, please revert it.)

      – T.J. Crowder
      Jan 4 at 12:23
















    4














    Just use the index and do the assignment directly:






    var a = ;
    

    
a[3] = "item-3";
    

    
console.log(a);








    share|improve this answer





















    • 2





      (As always: Hope my edit is helpful, but if not, please revert it.)

      – T.J. Crowder
      Jan 4 at 12:23














    4












    4








    4







    Just use the index and do the assignment directly:






    var a = ;
    

    
a[3] = "item-3";
    

    
console.log(a);








    share|improve this answer















    Just use the index and do the assignment directly:






    var a = ;
    

    
a[3] = "item-3";
    

    
console.log(a);








    var a = ;
    

    
a[3] = "item-3";
    

    
console.log(a);





    var a = ;
    

    
a[3] = "item-3";
    

    
console.log(a);






    share|improve this answer














    share|improve this answer



    share|improve this answer








    edited Jan 4 at 12:23









    T.J. Crowder

    701k12412471341




    701k12412471341










    answered Jan 4 at 12:21









    Nina ScholzNina Scholz

    199k15111182




    199k15111182








    • 2





      (As always: Hope my edit is helpful, but if not, please revert it.)

      – T.J. Crowder
      Jan 4 at 12:23














    • 2





      (As always: Hope my edit is helpful, but if not, please revert it.)

      – T.J. Crowder
      Jan 4 at 12:23








    2




    2





    (As always: Hope my edit is helpful, but if not, please revert it.)

    – T.J. Crowder
    Jan 4 at 12:23





    (As always: Hope my edit is helpful, but if not, please revert it.)

    – T.J. Crowder
    Jan 4 at 12:23













    0














    Coming in for the ES6 solution:



    [...Array(3), 'item-3']
    
// [undefined, undefined, undefined, "item-3"]





    share|improve this answer




























      0














      Coming in for the ES6 solution:



      [...Array(3), 'item-3']
      
// [undefined, undefined, undefined, "item-3"]





      share|improve this answer


























        0












        0








        0







        Coming in for the ES6 solution:



        [...Array(3), 'item-3']
        
// [undefined, undefined, undefined, "item-3"]





        share|improve this answer













        Coming in for the ES6 solution:



        [...Array(3), 'item-3']
        
// [undefined, undefined, undefined, "item-3"]






        share|improve this answer












        share|improve this answer



        share|improve this answer










        answered Jan 4 at 12:25









        Simon MártonSimon Márton

        12628




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