Return unique array values from an array inside an array of objects

Question

I can\'t find a similar question and I\'m a bit stuck. I have the following JSON array:

[
    {
        \"Name\": \"element1\",
        \"Attributes\": [\"1\         


        

Answer 1

With ES6/ES2015 you can use Set and the spread operator:

const input = [
    {
        "Name": "element1",
        "Attributes": ["1", "2"]
    },

    {
        "Name": "element2",
        "Attributes": ["1","3" ]
    },
    {
        "Name": "element3",
        "Attributes": []
    }
];

const output = [...new Set([].concat(...input.map(item => item.Attributes)))];

console.log(output);

Explanation (from the inside out):

• input.map(item => item.Attributes) produces an array of the Attributes arrays
• [].concat(...) flattens the arrays, i.e. produces an array of all the Attributes values (including duplicates)
• new Set() produces a Set from the array, i.e. stores only the unique Attribute values
• [...] produces an array from the Set's values, i.e. produces an array of all unique Attribute values