How to concatinate string ang a num in js

Question

I have values like this

var npi = {
            code1: 'sm1',
            code2: 'sm8',
            code3: 'sm9',
            code4: ''
          }

I want to push first 3 items into an array

var arr = [];
for (var i =0;i< 3;i++) {
  arr.push(npi.code+''+i);
}

It says error npi.code is undefined since it is not considering npi.code1 instead npi.code.

Here i think its concat problem.Can anyone please suggest me help.Thanks.

Any reason why only the first 3? Could it be you only want the none empty onces? — Icepickle
– Icepickle, Commented Jul 11, 2017 at 10:40

Sagar V · Accepted Answer · 2017-07-11 10:40:57Z

3

npi.code+''+i won't work because there is no such key code+''+i . Instead you could access the key in this way npi['code'+i] (like accessing array using index).

Also in your code, the i start with 0 and code0 is undefined. So, i should start with 1

Try this one

var arr = [];
for (var i = 1;i <= 3;i++) {
  arr.push(npi['code'+i]);
}

edited Jul 11, 2017 at 10:40

Sagar V

12.5k8 gold badges46 silver badges71 bronze badges

answered Jul 11, 2017 at 10:32

Zaphiel

2933 silver badges11 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Liam MacDonald Over a year ago

Would need to start at 1, also good idea to explain what is happening + maybe explain Object.keys?

Zaphiel Over a year ago

I just edited the code for work true. Owner of question should edit for himself..

Icepickle Over a year ago

@SagarV It is true that he also could explain why the square brackets should be used, however then the answer from Durga should be updated/downvoted as well

Sagar V Over a year ago

@Icepickle Durga's answer -> donwvoted -> he edited it -> upvoted

Icepickle Over a year ago

@SagarV True :) I also upvoted both answers ;) Nice that you were so consistent

Durga · Accepted Answer · 2017-07-11 10:43:47Z

2

var npi = {
            code1: 'sm1',
            code2: 'sm8',
            code3: 'sm9',
            code4: ''
          }

var arr = [];
for (var i =1;i<= 3;i++) {
  arr.push(npi['code'+i]);
}
console.log(arr)

For your case Iterate from 1 to 3, and get value from obj like npi['code'+i], here you need to use bracket as Property_accessors, because it takes value as string.

edited Jul 11, 2017 at 10:43

answered Jul 11, 2017 at 10:35

Durga

15.6k2 gold badges31 silver badges55 bronze badges

Comments

Ionut Necula · Accepted Answer · 2017-07-11 11:10:31Z

2

You can use Object.keys() method and a forEach() loop:

var npi = {
  code1: 'sm1',
  code2: 'sm8',
  code3: 'sm9',
  code4: ''
}
var arr = [];

Object.keys(npi).forEach(function(key) {
    if(npi[key] != ''){
      arr.push(npi[key]);
    }
});
console.log(arr);

The Object.keys() method returns an array of a given object's own enumerable properties, in the same order as that provided by a for...in loop (the difference being that a for-in loop enumerates properties in the prototype chain as well).

The reason why your code is not working, is because when trying to get the values of an object using . notation, the property can't be a string(when you concatenate using +''+ you practically convert the object property into a string). String works only in case of []. For example:

arr.push(npi.code + '' + i); //returns undefined
arr.push(npi['code' + i]); //returns your value

edited Jul 11, 2017 at 11:10

answered Jul 11, 2017 at 10:39

Ionut Necula

11.6k4 gold badges49 silver badges72 bronze badges

8 Comments

Ionut Necula Over a year ago

@SagarV, oh, ok, you're right. Corrected my answer accordingly.

Icepickle Over a year ago

Actually, you didn't, you only excluded possible empty values (which was not the question)

Sagar V Over a year ago

I retracted the vote. But FYI you should break it when it complete 3 iterations.

Ionut Necula Over a year ago

I understand what you're saying, but where is the logic?! I think that what the OP is intending, is to push non-empty elements into the new array. The original array may contain multiple elements, not just 4. I think my example applies on more levels and is more dynamic. You can give as many downvotes as you want, but I think this is the better answer.

Ionut Necula Over a year ago

@SagarV, oh, ok. Sorry for that. My bad.

|

TamerB · Accepted Answer · 2017-07-11 11:03:12Z

1

First of all, if you would like to append to the object key, you should use npi['code' + i] instead of npi.code+i. Because npi.code+i means appending the value of (i) to the value of the key (code) in npi, which doesn't exist.

Second of all, you should loop starting from i = 1 instead of i = 0. So that the loop starts with npi['code1'] not npi['code0'] which also doesn't exist.

Also, the loop condition should be i < 4 instead of i < 3 so that the loop ends after i = 3 instead of i = 2

var arr = [];

for (var i = 1 ; i < 4 ; i++) {
    arr.push(npi['code' + i]);
}
console.log(arr);

edited Jul 11, 2017 at 11:03

answered Jul 11, 2017 at 10:57

TamerB

1,4411 gold badge13 silver badges28 bronze badges

Comments

Liyaquet Hussain · Accepted Answer · 2017-07-11 11:46:31Z

0

Try This

var arr = [];
for (var i =0;i< 3;i++) {
  arr.push(npi['code'+i]);
}

answered Jul 11, 2017 at 11:46

Liyaquet Hussain

1015 bronze badges

Collectives™ on Stack Overflow

How to concatinate string ang a num in js

5 Answers 5

5 Comments

Comments

8 Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

5 Comments

Comments

8 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related