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Cover image for Merging array tables in JS
Marc Garcia i Mullon
Marc Garcia i Mullon

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Merging array tables in JS

#javascript #algorithms

Problem

We need to merge all this arrays into one big object.
First line of every array is the table headings, followed by users data.

  const arr1 = [
    ["name", "id", "age", "weight", "Cool"],
    ["Susan", "3", "20", "120", true],
    ["John", "1", "21", "150", true],
    ["Bob", "2", "23", "90", false],
    ["Ben", "4", "20", "100", true],
  ];

  const arr2 = [
    ["name", "id", "height"],
    ["Bob", "2", "50"],
    ["John", "1", "45"],
    ["Ben", "4", "43"],
    ["Susan", "3", "48"]
  ];

  const arr3 = [
    ["name", "id", "parent"],
    ["Bob", "2", "yes"],
    ["John", "1", "yes"]
  ];
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My proposal: 

const data = {};

function addData(arr, uuid = 'id'){
    const [headings, ...body] = arr;
    for(const elem of body){
        let id;
        let person = {};
        for(const [index, heading] of headings.entries()){
            if(heading === uuid){
                id = elem[index];
            }
            person[heading] = elem[index];
        }
        data[id] = {...data[id], ...person};
    }
}

addData(arr1);
addData(arr2);
addData(arr3);
console.table(data);
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Can you improve it? Do you have a different solution?
Let me know in comments!

Top comments (1)

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drarig29 profile image
Corentin Girard •

I used the same names for variables. I don't like messing with global variables very much, so I made a makeData() function, which is a pure function.

Then I made a replacement addData() function to have the same functionality as your code. You can use it the same way 😄

function makeData(arr, uuid = 'id') {
    const [headings, ...body] = arr;
    const idPosition = headings.indexOf(uuid);

    return body.reduce((data, elem) => ({
        ...data, ...{
            [elem[idPosition]]: Object.fromEntries(elem.map((value, index) => [headings[index], value]))
        }
    }), {});
}

function addData(arr, uuid = 'id') {
    Object.assign(data, makeData(arr, uuid));
}
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