How to merge and return new array from object in es6How can I merge properties of two JavaScript objects...

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How to merge and return new array from object in es6


How can I merge properties of two JavaScript objects dynamically?How do I remove a property from a JavaScript object?How do I check if an array includes an object in JavaScript?How to append something to an array?How to insert an item into an array at a specific index (JavaScript)?How do I correctly clone a JavaScript object?Sort array of objects by string property valueHow to check if an object is an array?How do I remove a particular element from an array in JavaScript?How do I return the response from an asynchronous call?













11















Suppose there are two objects.



const a = [
{ id: '1-1-1', name: 'a111' },
{ id: '1-1-2', name: 'a112' },
{ id: '1-2-1', name: 'a121' },
{ id: '1-2-2', name: 'a122' },
{ id: '2-1-1', name: 'a211' },
{ id: '2-1-2', name: 'a212' }
]
const b = ['1-1', '1-2', '2-1']


and the result



  {

'1-1':[
{ id: '1-1-1', name: 'a111' },
{ id: '1-1-2', name: 'a112' },
],
'1-2':[
{ id: '1-2-1', name: 'a121' },
{ id: '1-2-2', name: 'a122' },
],
'2-1':[
{ id: '2-1-1', name: 'a211' },
{ id: '2-1-2', name: 'a212' },
]
}


Basically, I want to group the data.



I use includes to check if the item from b to match the id from a. Then construct the new array.



This is my attempt(fiddle):



return b.map(item => a.map(jtem => {
if(jtem.id.includes(item)){
return {
[item]: jtem
}
}
}))


For somehow, it doesn't work.



and, is there a clever way to avoid the nested for loop or map function?










share|improve this question

























  • Shouldn't the result be an object?

    – Jack Bashford
    23 hours ago











  • @JackBashford Hey man, sry, u r right, I just updated it.

    – SPG
    23 hours ago











  • Do you really want includes? I'd recommend startsWith

    – Bergi
    21 hours ago











  • @Bergi thx, I think startWith is better

    – SPG
    5 hours ago
















11















Suppose there are two objects.



const a = [
{ id: '1-1-1', name: 'a111' },
{ id: '1-1-2', name: 'a112' },
{ id: '1-2-1', name: 'a121' },
{ id: '1-2-2', name: 'a122' },
{ id: '2-1-1', name: 'a211' },
{ id: '2-1-2', name: 'a212' }
]
const b = ['1-1', '1-2', '2-1']


and the result



  {

'1-1':[
{ id: '1-1-1', name: 'a111' },
{ id: '1-1-2', name: 'a112' },
],
'1-2':[
{ id: '1-2-1', name: 'a121' },
{ id: '1-2-2', name: 'a122' },
],
'2-1':[
{ id: '2-1-1', name: 'a211' },
{ id: '2-1-2', name: 'a212' },
]
}


Basically, I want to group the data.



I use includes to check if the item from b to match the id from a. Then construct the new array.



This is my attempt(fiddle):



return b.map(item => a.map(jtem => {
if(jtem.id.includes(item)){
return {
[item]: jtem
}
}
}))


For somehow, it doesn't work.



and, is there a clever way to avoid the nested for loop or map function?










share|improve this question

























  • Shouldn't the result be an object?

    – Jack Bashford
    23 hours ago











  • @JackBashford Hey man, sry, u r right, I just updated it.

    – SPG
    23 hours ago











  • Do you really want includes? I'd recommend startsWith

    – Bergi
    21 hours ago











  • @Bergi thx, I think startWith is better

    – SPG
    5 hours ago














11












11








11


1






Suppose there are two objects.



const a = [
{ id: '1-1-1', name: 'a111' },
{ id: '1-1-2', name: 'a112' },
{ id: '1-2-1', name: 'a121' },
{ id: '1-2-2', name: 'a122' },
{ id: '2-1-1', name: 'a211' },
{ id: '2-1-2', name: 'a212' }
]
const b = ['1-1', '1-2', '2-1']


and the result



  {

'1-1':[
{ id: '1-1-1', name: 'a111' },
{ id: '1-1-2', name: 'a112' },
],
'1-2':[
{ id: '1-2-1', name: 'a121' },
{ id: '1-2-2', name: 'a122' },
],
'2-1':[
{ id: '2-1-1', name: 'a211' },
{ id: '2-1-2', name: 'a212' },
]
}


Basically, I want to group the data.



I use includes to check if the item from b to match the id from a. Then construct the new array.



This is my attempt(fiddle):



return b.map(item => a.map(jtem => {
if(jtem.id.includes(item)){
return {
[item]: jtem
}
}
}))


For somehow, it doesn't work.



and, is there a clever way to avoid the nested for loop or map function?










share|improve this question
















Suppose there are two objects.



const a = [
{ id: '1-1-1', name: 'a111' },
{ id: '1-1-2', name: 'a112' },
{ id: '1-2-1', name: 'a121' },
{ id: '1-2-2', name: 'a122' },
{ id: '2-1-1', name: 'a211' },
{ id: '2-1-2', name: 'a212' }
]
const b = ['1-1', '1-2', '2-1']


and the result



  {

'1-1':[
{ id: '1-1-1', name: 'a111' },
{ id: '1-1-2', name: 'a112' },
],
'1-2':[
{ id: '1-2-1', name: 'a121' },
{ id: '1-2-2', name: 'a122' },
],
'2-1':[
{ id: '2-1-1', name: 'a211' },
{ id: '2-1-2', name: 'a212' },
]
}


Basically, I want to group the data.



I use includes to check if the item from b to match the id from a. Then construct the new array.



This is my attempt(fiddle):



return b.map(item => a.map(jtem => {
if(jtem.id.includes(item)){
return {
[item]: jtem
}
}
}))


For somehow, it doesn't work.



and, is there a clever way to avoid the nested for loop or map function?







javascript ecmascript-6 ecmascript-7






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited 23 hours ago







SPG

















asked 23 hours ago









SPGSPG

2,439103359




2,439103359













  • Shouldn't the result be an object?

    – Jack Bashford
    23 hours ago











  • @JackBashford Hey man, sry, u r right, I just updated it.

    – SPG
    23 hours ago











  • Do you really want includes? I'd recommend startsWith

    – Bergi
    21 hours ago











  • @Bergi thx, I think startWith is better

    – SPG
    5 hours ago



















  • Shouldn't the result be an object?

    – Jack Bashford
    23 hours ago











  • @JackBashford Hey man, sry, u r right, I just updated it.

    – SPG
    23 hours ago











  • Do you really want includes? I'd recommend startsWith

    – Bergi
    21 hours ago











  • @Bergi thx, I think startWith is better

    – SPG
    5 hours ago

















Shouldn't the result be an object?

– Jack Bashford
23 hours ago





Shouldn't the result be an object?

– Jack Bashford
23 hours ago













@JackBashford Hey man, sry, u r right, I just updated it.

– SPG
23 hours ago





@JackBashford Hey man, sry, u r right, I just updated it.

– SPG
23 hours ago













Do you really want includes? I'd recommend startsWith

– Bergi
21 hours ago





Do you really want includes? I'd recommend startsWith

– Bergi
21 hours ago













@Bergi thx, I think startWith is better

– SPG
5 hours ago





@Bergi thx, I think startWith is better

– SPG
5 hours ago












1 Answer
1






active

oldest

votes


















14














You can do that in following steps:




  • Apply reduce() on the array b


  • During each iteration use filter() on the the array a


  • Get all the items from a which starts with item of b using String.prototype.startsWith()

  • At last set it as property of the ac and return ac





const a = [
{ id: '1-1-1', name: 'a111' },
{ id: '1-1-2', name: 'a112' },
{ id: '1-2-1', name: 'a121' },
{ id: '1-2-2', name: 'a122' },
{ id: '2-1-1', name: 'a211' },
{ id: '2-1-2', name: 'a212' }
]
const b = ['1-1', '1-2', '2-1']

let res = b.reduce((ac,b) => {

ac[b] = a.filter(x => x.id.startsWith(b));
return ac;

},{})
console.log(res)





As suggested by @Falco is the comments that It would be better to scan over the a once as its large. So here is that version.Actually its better regarding performance






const a = [
{ id: '1-1-1', name: 'a111' },
{ id: '1-1-2', name: 'a112' },
{ id: '1-2-1', name: 'a121' },
{ id: '1-2-2', name: 'a122' },
{ id: '2-1-1', name: 'a211' },
{ id: '2-1-2', name: 'a212' }
]
const b = ['1-1', '1-2', '2-1']


let res = a.reduce((ac,x) => {
let temp = b.find(y => x.id.startsWith(y))
if(!ac[temp]) ac[temp] = [];
ac[temp].push(x);
return ac;
},{})

console.log(res)





Note: startsWith is not supported by I.E. So you can create polyfill using indexOf






if(!String.prototype.startWith){
String.prototype.startsWith = function(str){
return this.indexOf(str) === 0
}
}








share|improve this answer





















  • 1





    While it is specifically said in the question that the op wants to use es6, and that IE don't support es6 features, I just want to mention that startsWith() don't work in IE (while reduce, filter, and setting a property of an object is totally fine if IE > 9) and if someone wants to do the same thing that startsWith do, they can implment their own with some substring :)

    – Neyt
    20 hours ago











  • For big a and small b I would probably go with a.reduce(...) because of locality and only scan over the big array once.

    – Falco
    18 hours ago











  • @Falco Thanks for suggestion I updated.

    – Maheer Ali
    18 hours ago






  • 1





    @Neyt Thanks for suggestion I updated

    – Maheer Ali
    18 hours ago











  • @MaheerAli Thank you - here is a benchmark comparing the two :-) jsbench.me/dfjtoadysr/1

    – Falco
    18 hours ago











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1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









14














You can do that in following steps:




  • Apply reduce() on the array b


  • During each iteration use filter() on the the array a


  • Get all the items from a which starts with item of b using String.prototype.startsWith()

  • At last set it as property of the ac and return ac





const a = [
{ id: '1-1-1', name: 'a111' },
{ id: '1-1-2', name: 'a112' },
{ id: '1-2-1', name: 'a121' },
{ id: '1-2-2', name: 'a122' },
{ id: '2-1-1', name: 'a211' },
{ id: '2-1-2', name: 'a212' }
]
const b = ['1-1', '1-2', '2-1']

let res = b.reduce((ac,b) => {

ac[b] = a.filter(x => x.id.startsWith(b));
return ac;

},{})
console.log(res)





As suggested by @Falco is the comments that It would be better to scan over the a once as its large. So here is that version.Actually its better regarding performance






const a = [
{ id: '1-1-1', name: 'a111' },
{ id: '1-1-2', name: 'a112' },
{ id: '1-2-1', name: 'a121' },
{ id: '1-2-2', name: 'a122' },
{ id: '2-1-1', name: 'a211' },
{ id: '2-1-2', name: 'a212' }
]
const b = ['1-1', '1-2', '2-1']


let res = a.reduce((ac,x) => {
let temp = b.find(y => x.id.startsWith(y))
if(!ac[temp]) ac[temp] = [];
ac[temp].push(x);
return ac;
},{})

console.log(res)





Note: startsWith is not supported by I.E. So you can create polyfill using indexOf






if(!String.prototype.startWith){
String.prototype.startsWith = function(str){
return this.indexOf(str) === 0
}
}








share|improve this answer





















  • 1





    While it is specifically said in the question that the op wants to use es6, and that IE don't support es6 features, I just want to mention that startsWith() don't work in IE (while reduce, filter, and setting a property of an object is totally fine if IE > 9) and if someone wants to do the same thing that startsWith do, they can implment their own with some substring :)

    – Neyt
    20 hours ago











  • For big a and small b I would probably go with a.reduce(...) because of locality and only scan over the big array once.

    – Falco
    18 hours ago











  • @Falco Thanks for suggestion I updated.

    – Maheer Ali
    18 hours ago






  • 1





    @Neyt Thanks for suggestion I updated

    – Maheer Ali
    18 hours ago











  • @MaheerAli Thank you - here is a benchmark comparing the two :-) jsbench.me/dfjtoadysr/1

    – Falco
    18 hours ago
















14














You can do that in following steps:




  • Apply reduce() on the array b


  • During each iteration use filter() on the the array a


  • Get all the items from a which starts with item of b using String.prototype.startsWith()

  • At last set it as property of the ac and return ac





const a = [
{ id: '1-1-1', name: 'a111' },
{ id: '1-1-2', name: 'a112' },
{ id: '1-2-1', name: 'a121' },
{ id: '1-2-2', name: 'a122' },
{ id: '2-1-1', name: 'a211' },
{ id: '2-1-2', name: 'a212' }
]
const b = ['1-1', '1-2', '2-1']

let res = b.reduce((ac,b) => {

ac[b] = a.filter(x => x.id.startsWith(b));
return ac;

},{})
console.log(res)





As suggested by @Falco is the comments that It would be better to scan over the a once as its large. So here is that version.Actually its better regarding performance






const a = [
{ id: '1-1-1', name: 'a111' },
{ id: '1-1-2', name: 'a112' },
{ id: '1-2-1', name: 'a121' },
{ id: '1-2-2', name: 'a122' },
{ id: '2-1-1', name: 'a211' },
{ id: '2-1-2', name: 'a212' }
]
const b = ['1-1', '1-2', '2-1']


let res = a.reduce((ac,x) => {
let temp = b.find(y => x.id.startsWith(y))
if(!ac[temp]) ac[temp] = [];
ac[temp].push(x);
return ac;
},{})

console.log(res)





Note: startsWith is not supported by I.E. So you can create polyfill using indexOf






if(!String.prototype.startWith){
String.prototype.startsWith = function(str){
return this.indexOf(str) === 0
}
}








share|improve this answer





















  • 1





    While it is specifically said in the question that the op wants to use es6, and that IE don't support es6 features, I just want to mention that startsWith() don't work in IE (while reduce, filter, and setting a property of an object is totally fine if IE > 9) and if someone wants to do the same thing that startsWith do, they can implment their own with some substring :)

    – Neyt
    20 hours ago











  • For big a and small b I would probably go with a.reduce(...) because of locality and only scan over the big array once.

    – Falco
    18 hours ago











  • @Falco Thanks for suggestion I updated.

    – Maheer Ali
    18 hours ago






  • 1





    @Neyt Thanks for suggestion I updated

    – Maheer Ali
    18 hours ago











  • @MaheerAli Thank you - here is a benchmark comparing the two :-) jsbench.me/dfjtoadysr/1

    – Falco
    18 hours ago














14












14








14







You can do that in following steps:




  • Apply reduce() on the array b


  • During each iteration use filter() on the the array a


  • Get all the items from a which starts with item of b using String.prototype.startsWith()

  • At last set it as property of the ac and return ac





const a = [
{ id: '1-1-1', name: 'a111' },
{ id: '1-1-2', name: 'a112' },
{ id: '1-2-1', name: 'a121' },
{ id: '1-2-2', name: 'a122' },
{ id: '2-1-1', name: 'a211' },
{ id: '2-1-2', name: 'a212' }
]
const b = ['1-1', '1-2', '2-1']

let res = b.reduce((ac,b) => {

ac[b] = a.filter(x => x.id.startsWith(b));
return ac;

},{})
console.log(res)





As suggested by @Falco is the comments that It would be better to scan over the a once as its large. So here is that version.Actually its better regarding performance






const a = [
{ id: '1-1-1', name: 'a111' },
{ id: '1-1-2', name: 'a112' },
{ id: '1-2-1', name: 'a121' },
{ id: '1-2-2', name: 'a122' },
{ id: '2-1-1', name: 'a211' },
{ id: '2-1-2', name: 'a212' }
]
const b = ['1-1', '1-2', '2-1']


let res = a.reduce((ac,x) => {
let temp = b.find(y => x.id.startsWith(y))
if(!ac[temp]) ac[temp] = [];
ac[temp].push(x);
return ac;
},{})

console.log(res)





Note: startsWith is not supported by I.E. So you can create polyfill using indexOf






if(!String.prototype.startWith){
String.prototype.startsWith = function(str){
return this.indexOf(str) === 0
}
}








share|improve this answer















You can do that in following steps:




  • Apply reduce() on the array b


  • During each iteration use filter() on the the array a


  • Get all the items from a which starts with item of b using String.prototype.startsWith()

  • At last set it as property of the ac and return ac





const a = [
{ id: '1-1-1', name: 'a111' },
{ id: '1-1-2', name: 'a112' },
{ id: '1-2-1', name: 'a121' },
{ id: '1-2-2', name: 'a122' },
{ id: '2-1-1', name: 'a211' },
{ id: '2-1-2', name: 'a212' }
]
const b = ['1-1', '1-2', '2-1']

let res = b.reduce((ac,b) => {

ac[b] = a.filter(x => x.id.startsWith(b));
return ac;

},{})
console.log(res)





As suggested by @Falco is the comments that It would be better to scan over the a once as its large. So here is that version.Actually its better regarding performance






const a = [
{ id: '1-1-1', name: 'a111' },
{ id: '1-1-2', name: 'a112' },
{ id: '1-2-1', name: 'a121' },
{ id: '1-2-2', name: 'a122' },
{ id: '2-1-1', name: 'a211' },
{ id: '2-1-2', name: 'a212' }
]
const b = ['1-1', '1-2', '2-1']


let res = a.reduce((ac,x) => {
let temp = b.find(y => x.id.startsWith(y))
if(!ac[temp]) ac[temp] = [];
ac[temp].push(x);
return ac;
},{})

console.log(res)





Note: startsWith is not supported by I.E. So you can create polyfill using indexOf






if(!String.prototype.startWith){
String.prototype.startsWith = function(str){
return this.indexOf(str) === 0
}
}








const a = [
{ id: '1-1-1', name: 'a111' },
{ id: '1-1-2', name: 'a112' },
{ id: '1-2-1', name: 'a121' },
{ id: '1-2-2', name: 'a122' },
{ id: '2-1-1', name: 'a211' },
{ id: '2-1-2', name: 'a212' }
]
const b = ['1-1', '1-2', '2-1']

let res = b.reduce((ac,b) => {

ac[b] = a.filter(x => x.id.startsWith(b));
return ac;

},{})
console.log(res)





const a = [
{ id: '1-1-1', name: 'a111' },
{ id: '1-1-2', name: 'a112' },
{ id: '1-2-1', name: 'a121' },
{ id: '1-2-2', name: 'a122' },
{ id: '2-1-1', name: 'a211' },
{ id: '2-1-2', name: 'a212' }
]
const b = ['1-1', '1-2', '2-1']

let res = b.reduce((ac,b) => {

ac[b] = a.filter(x => x.id.startsWith(b));
return ac;

},{})
console.log(res)





const a = [
{ id: '1-1-1', name: 'a111' },
{ id: '1-1-2', name: 'a112' },
{ id: '1-2-1', name: 'a121' },
{ id: '1-2-2', name: 'a122' },
{ id: '2-1-1', name: 'a211' },
{ id: '2-1-2', name: 'a212' }
]
const b = ['1-1', '1-2', '2-1']


let res = a.reduce((ac,x) => {
let temp = b.find(y => x.id.startsWith(y))
if(!ac[temp]) ac[temp] = [];
ac[temp].push(x);
return ac;
},{})

console.log(res)





const a = [
{ id: '1-1-1', name: 'a111' },
{ id: '1-1-2', name: 'a112' },
{ id: '1-2-1', name: 'a121' },
{ id: '1-2-2', name: 'a122' },
{ id: '2-1-1', name: 'a211' },
{ id: '2-1-2', name: 'a212' }
]
const b = ['1-1', '1-2', '2-1']


let res = a.reduce((ac,x) => {
let temp = b.find(y => x.id.startsWith(y))
if(!ac[temp]) ac[temp] = [];
ac[temp].push(x);
return ac;
},{})

console.log(res)





if(!String.prototype.startWith){
String.prototype.startsWith = function(str){
return this.indexOf(str) === 0
}
}





if(!String.prototype.startWith){
String.prototype.startsWith = function(str){
return this.indexOf(str) === 0
}
}






share|improve this answer














share|improve this answer



share|improve this answer








edited 14 hours ago

























answered 23 hours ago









Maheer AliMaheer Ali

7,451619




7,451619








  • 1





    While it is specifically said in the question that the op wants to use es6, and that IE don't support es6 features, I just want to mention that startsWith() don't work in IE (while reduce, filter, and setting a property of an object is totally fine if IE > 9) and if someone wants to do the same thing that startsWith do, they can implment their own with some substring :)

    – Neyt
    20 hours ago











  • For big a and small b I would probably go with a.reduce(...) because of locality and only scan over the big array once.

    – Falco
    18 hours ago











  • @Falco Thanks for suggestion I updated.

    – Maheer Ali
    18 hours ago






  • 1





    @Neyt Thanks for suggestion I updated

    – Maheer Ali
    18 hours ago











  • @MaheerAli Thank you - here is a benchmark comparing the two :-) jsbench.me/dfjtoadysr/1

    – Falco
    18 hours ago














  • 1





    While it is specifically said in the question that the op wants to use es6, and that IE don't support es6 features, I just want to mention that startsWith() don't work in IE (while reduce, filter, and setting a property of an object is totally fine if IE > 9) and if someone wants to do the same thing that startsWith do, they can implment their own with some substring :)

    – Neyt
    20 hours ago











  • For big a and small b I would probably go with a.reduce(...) because of locality and only scan over the big array once.

    – Falco
    18 hours ago











  • @Falco Thanks for suggestion I updated.

    – Maheer Ali
    18 hours ago






  • 1





    @Neyt Thanks for suggestion I updated

    – Maheer Ali
    18 hours ago











  • @MaheerAli Thank you - here is a benchmark comparing the two :-) jsbench.me/dfjtoadysr/1

    – Falco
    18 hours ago








1




1





While it is specifically said in the question that the op wants to use es6, and that IE don't support es6 features, I just want to mention that startsWith() don't work in IE (while reduce, filter, and setting a property of an object is totally fine if IE > 9) and if someone wants to do the same thing that startsWith do, they can implment their own with some substring :)

– Neyt
20 hours ago





While it is specifically said in the question that the op wants to use es6, and that IE don't support es6 features, I just want to mention that startsWith() don't work in IE (while reduce, filter, and setting a property of an object is totally fine if IE > 9) and if someone wants to do the same thing that startsWith do, they can implment their own with some substring :)

– Neyt
20 hours ago













For big a and small b I would probably go with a.reduce(...) because of locality and only scan over the big array once.

– Falco
18 hours ago





For big a and small b I would probably go with a.reduce(...) because of locality and only scan over the big array once.

– Falco
18 hours ago













@Falco Thanks for suggestion I updated.

– Maheer Ali
18 hours ago





@Falco Thanks for suggestion I updated.

– Maheer Ali
18 hours ago




1




1





@Neyt Thanks for suggestion I updated

– Maheer Ali
18 hours ago





@Neyt Thanks for suggestion I updated

– Maheer Ali
18 hours ago













@MaheerAli Thank you - here is a benchmark comparing the two :-) jsbench.me/dfjtoadysr/1

– Falco
18 hours ago





@MaheerAli Thank you - here is a benchmark comparing the two :-) jsbench.me/dfjtoadysr/1

– Falco
18 hours ago




















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