How to split one object with an array in it to multiple objects

Question

I want to know if there is it is possible to split up an object into multiple objects. I have an array of objects that has another array in it and I was wondering if it is possible to split those objects for each object in the inner array. Something like:

obj1 = [{
  a: 1,
  b: [{c: 2},{d: 3}],
  e: 4
}]

to

obj2 =[
  {
    a: 1,
    b: [{c: 2}],
    e: 4
  },
  {
    a: 1,
    b: [{d: 3}],
    e: 4
  }
]

The object is always in this form, whether it has one object or hundreds. While some objects may have more fields in them, there is only one field with an array. Currently, I am mapping across the original array and then mapping again inside the b array to get to each object in there. However, I do not know where to go from there as the return object from that map would just be the original array. I do not know how to split the b array and map it with the original one. I thought of {...orig, b: map()} but I don't think it will work with every object

Please indicate if the structure of your object is always like that as well as what you have tried so far to make it work. — M0nst3R
– M0nst3R, Commented Sep 25, 2019 at 20:55
Welcome to Stackoverflow, please read How To Ask. Pay special attention to How To Create MCVE. Make sure you tag your question with proper labels (programming language, relevant technologies etc). The more effort you'll put into posting a good question: one which is easy to read, understand and which is on topic - the chances are higher that it will attract the relevant people and you'll get help even faster. Good luck! — Nir Alfasi
– Nir Alfasi, Commented Sep 25, 2019 at 21:00
@GhassenLouhaichi edited what I tried. I thought about mapping through it but struggled to put the mapping back together — H. Manner
– H. Manner, Commented Sep 25, 2019 at 21:07
Can there be other attributes in your source object than just a and b? Also, can there be more than one element in your source array? — M0nst3R
– M0nst3R, Commented Sep 25, 2019 at 21:26
@GhassenLouhaichi there can be more elements in the source object, and there can more more elements in the source array. However, I would only want to split b if it has more than one element — H. Manner
– H. Manner, Commented Sep 25, 2019 at 21:57

M0nst3R · Accepted Answer · 2019-09-25 21:58:07Z

You were on the right track according to the description in your post. You have to loop through your source object, and inside each iteration, loop through your b array to extract each element and push it with the source iteration element in a new object into a target array.

var source = [{
    a: 1,
    b: [{ c: 2 }, { d: 3 }],
    e: 4
}];

// define target as an array
var target = [];

// loop through source
source.forEach((srcElement) => {
    // loop through `b` array attribute
    srcElement.b.forEach((bElement) => {
        // push object into target with source element attributes
        // and current `b` element wrapped into an array
        target.push({
            ...srcElement,
            b: [bElement]
        });
    });
});

console.log(target);

NOTE: this solution assumes that on each iteration on your source object, the b attribute exists and is of type Array.

Thanks! The part of where to save the new object was driving me nuts!

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