How to get the combination of array values from nested arrays in an array of objects

Question

I have an array of objects with the following structure:

 var varientSections = [
  {
    type: "frame",
    values: ["black", "white", "wood"]
  },
  {
    type: "finish",
    values: ["matte", "glossy"]
  }
];

I want to get the combination of the array values and create a new list with it. Right now, I am able to retrieve the combination from the nested array values using the method called getCombination(varientSections). However, I do not know how to create a new list with the following structure:

var results = [
  {
    attributes: [
      {
        type: "frame",
        value: "black"
      },
      {
        type: "finish",
        value: "matte"
      }
    ]
  },
  {
    attributes: [
      {
        type: "frame",
        value: "black"
      },
      {
        type: "finish",
        value: "glossy"
      }
    ]
  },
  {
    attributes: [
      {
        type: "frame",
        value: "white"
      },
      {
        type: "finish",
        value: "matte"
      }
    ]
  },
  {
    attributes: [
      {
        type: "frame",
        value: "white"
      },
      {
        type: "finish",
        value: "glossy"
      }
    ]
  },
  {
    attributes: [
      {
        type: "frame",
        value: "wood"
      },
      {
        type: "finish",
        value: "matte"
      }
    ]
  },
  {
    attributes: [
      {
        type: "frame",
        value: "wood"
      },
      {
        type: "finish",
        value: "glossy"
      }
    ]
  }
];

Below is my code:

function getCombinations(arr) {
  if (arr.length === 0) {
    return [[]];
  }

  let [current, ...rest] = arr;
  let combinations = getCombinations(rest);

  var result = current.values.reduce(
    (accumulator, currentValue) => [
      ...accumulator,
      ...combinations.map(c => [currentValue, ...c])
    ],
    []
  );
  console.log("result is ");
  console.log(result);
  return result;
}

let varientCombinations = getCombinations(varientSections);
console.log(varientCombinations);

let updatedVarientDetails = [];
varientSections.forEach((varientSection, index) => {
  let type = varientSection.type;
  varientCombinations.forEach(combination => {
    let obj = [
      {
        type: type,
        value: combination[index]
      },
    ];
    updatedVarientDetails.push(obj);
  });
});

console.log(updatedVarientDetails);

Hi @MaikenMadsen thanks for the reply. What do you mean? I am open to any method! I just want to produce the list with the following structure that I mentioned above. — Issaki
– Issaki, Commented Jul 10, 2019 at 13:47
Here is a simple example from w3school: w3schools.com/jsref/jsref_concat_array.asp — Maiken Madsen
– Maiken Madsen, Commented Jul 10, 2019 at 13:52

Nina Scholz · Accepted Answer · 2019-07-10 14:16:09Z

You could get the cartesian product and give it later the wanted style. The names and values are taken form the handed over object.

The algorithm takes all key/value pairs and has a stric view to the values, that means if an array is found or an object, hence w && typeof w === "object", the actual part is taken an used for adding additional key/value pairs.

For example a small object with two properties

{ a: 1, b: [2, 3] }

yields

[
    { a: 1, b: 2 },
    { a: 1, b: 3 }
]

A bit more advanced object, like

{ a: 1, b: { c: { d: [2, 3], e: [4, 5] } } }

yields the same structure as given

[
    {
        a: 1,
        b: {
            c: { d: 2, e: 4 }
        }
    },
    {
        a: 1,
        b: {
            c: { d: 2, e: 5 }
        }
    },
    {
        a: 1,
        b: {
            c: { d: 3, e: 4 }
        }
    },
    {
        a: 1,
        b: {
            c: { d: 3, e: 5 }
        }
    }
]

Thant means, from any found sub object the cartesian product is taken and combined with the actual values.

const
    getCartesian = object => Object.entries(object).reduce(
        (r, [key, value]) => {
            let temp = [];
            r.forEach(s =>
                (Array.isArray(value) ? value : [value]).forEach(w =>
                    (w && typeof w === "object" ? getCartesian(w) : [w]).forEach(x =>
                        temp.push({ ...s, [key]: x })
                    )
                )
            );
            return temp;
        },
        [{}]
    ),
    data = [{ type: "frame", value: ["black", "white", "wood"] }, { type: "finish", value: ["matte", "glossy"] }],
    result = getCartesian(data)
        .map(o => ({ attributes: Object.assign([], o).map(({ ...o }) => o) }));

console.log(result);

console.log(getCartesian({ a: 1, b: { c: { d: [2, 3], e: [4, 5] } } }));

.as-console-wrapper { max-height: 100% !important; top: 0; }

Is it possible if you can write some comment for me to understand?

Nick G · Accepted Answer · 2019-07-10 14:01:21Z

3

You could simplify it to this:

var variantSections = [
  {
    type: "frame",
    values: ["black", "white", "wood"]
  },
  {
    type: "finish",
    values: ["matte", "glossy"]
  }
];

// iterate through each variantSection and create objects like {"type": "frame", "value": "black"}
var sections = variantSections.map(variant => {
	return variant.values.map(val => ({type: variant.type, value: val}))
});

// then iterate through the two resulting arrays of objects, combining each into the attributes object you want
var results = [];
for (var i = 0; i < sections[0].length; i++) {
	for (var j = 0; j < sections[1].length; j++) {
		results.push({attributes: [sections[0][i], sections[1][j]]});
	}
}

console.log(JSON.parse(JSON.stringify(results)));

edited Jul 10, 2019 at 14:01

answered Jul 10, 2019 at 13:55

Nick G

1,98314 silver badges17 bronze badges

1 Comment

Issaki Over a year ago

Hi @Nick G, thanks for the reply! I really appreciate it. However, Nina Scholz answered a few mins before you. Hence, I accepted his answer. Thanks once again!

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