Splitting an array remains as array of one item rather than a string

Question

I have a javascript array of objects, where there is a property with another array as value, as seen here:

var data = [
{
id: 1,
parent: [1,2,3,4]
}, 
{
id: 2,
parent: [5,6,7,8]
}
]

I am trying to split it, so every object with more than one parent, gets a duplicated copy of itself, each copy with a different parent. I have done this so far:

var updateddata = JSON.parse(JSON.stringify(data));

for (var i = 0; i < updateddata[i].parent.length; i++) {
    while (updateddata[i].parent.length > 1) {
        updateddata.push({
        id: updateddata[i].id,
        parent: updateddata[i].parent[0]
    })
updateddata[i].parent.shift()
}
}

And it works perfect, except for the fact that when doing console.log(JSON.stringify(updateddata)) I can see that the first two entries have as a parent an array with one single entry, unlike the others, which are already outside the array:

This is the console.log for updateddata:

[
{"id":1,"parent":[4]},
{"id":2,"parent":[8]},
{"id":1,"parent":1},
{"id":1,"parent":2},
{"id":1,"parent":3},
{"id":2,"parent":5},
{"id":2,"parent":6},
{"id":2,"parent":7}
]

I have also tried to use .toString() in the values, but it didn't make any difference.

How could I solve it?

You should do your while loop until 0, since you are not checking if length equals 0. You are not reading the last one. — AxelH
– AxelH, Commented Aug 16, 2016 at 11:06

Nenad Vracar · Accepted Answer · 2016-08-16 11:18:49Z

1

You could do this with reduce() and forEach() loop

var data = [{
  id: 1,
  parent: [1, 2, 3, 4]
}, {
  id: 2,
  parent: [5, 6, 7, 8]
}]

var result = data.reduce(function(r, ar) {
  ar.parent.forEach(function(e) {
    r.push({id: ar.id, parent: e});
  });
  return r;
}, []);

console.log(result)

answered Aug 16, 2016 at 11:18

Nenad Vracar

122k16 gold badges160 silver badges184 bronze badges

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

1 Comment

telex-wap Over a year ago

Thanks. It works well. I decided to accept this answer, as the method you use is interesting and I didn't know it, so I will keep reading about that.

Paweł Mikołajczyk · Accepted Answer · 2016-08-16 11:06:30Z

1

Is it what you needed?

var data = [
{
id: 1,
parent: [1,2,3,4]
}, 
{
id: 2,
parent: [5,6,7,8]
}
]

var updatedData = [];

data.forEach((obj) => {
  if (obj.parent.length > 1) {
    obj.parent.forEach((value) => {
      updatedData.push({
        id: obj.id,
        parent: [value]
      });
    })
  }
});

answered Aug 16, 2016 at 11:06

Paweł Mikołajczyk

3811 gold badge2 silver badges14 bronze badges

1 Comment

telex-wap Over a year ago

Thanks. It should be parent: value instead, as I wanted the value outside the array, but this is pretty much it.

Shwetha · Accepted Answer · 2016-08-16 11:53:35Z

1

Here we can use for loop to traverse the array:

var data = [
{
id: 1,
parent: [1,2,3,4]
}, 
{
id: 2,
parent: [5,6,7,8]
}
];
var result = [];
for(var i=0; i<data.length; i++) {
    var obj = data[i];
    for(var j=0;j<obj.parent.length; j++) {
        result.push({id: obj["id"], parent: obj.parent[j]});
    }
}
console.log(result);

THe result will print the expected result.

answered Aug 16, 2016 at 11:53

Shwetha

9138 silver badges15 bronze badges

Comments

AxelH · Accepted Answer · 2016-08-16 12:50:11Z

1

I will still write the answer to use you code correctly since you had something working :

for (var i = 0; i < updateddata[i].parent.length; i++) {
    while (updateddata[i].parent.length > 0) { // Here you should read the last one
        updateddata.push({
        id: updateddata[i].id,
        parent: updateddata[i].parent[0]
        })
        updateddata[i].parent.shift()
    }
}

Of course this will keep the empty array at the beginning. Two solutions, remove after treatment or when length = 1 change parent array into the value

answered Aug 16, 2016 at 12:50

AxelH

14.6k2 gold badges27 silver badges56 bronze badges

Comments

Mulan · Accepted Answer · 2016-08-17 17:02:57Z

1

I think reduce, concat, and map yield a more declarative solution.

var data = [
  { id: 1, parent: [1,2,3,4] }, 
  { id: 2, parent: [5,6,7,8] }
]

let result = data.reduce((acc, {id, parent}) =>
  [...acc, ...parent.map(x => ({id, parent:x}))], [])
   
console.log(result)

If you define the shape of the output data ahead of time, it makes things a bit better yet

var data = [
  { id: 1, parent: [1,2,3,4] }, 
  { id: 2, parent: [5,6,7,8] }
]

let shape = id => parent => ({id, parent})

let result = data.reduce((acc, {id, parent}) =>
  [...acc, ...parent.map(shape(id))], [])
   
console.log(result)

edited Aug 17, 2016 at 17:02

answered Aug 16, 2016 at 19:39

Mulan

136k35 gold badges240 silver badges276 bronze badges

Collectives™ on Stack Overflow

Splitting an array remains as array of one item rather than a string

5 Answers 5

1 Comment

1 Comment

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

1 Comment

1 Comment

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related