Logic to create array of array in JavaScript

Question

I have a little problem with this logic. I need to create a dynamic Array of Array. But the last object in every Array is not correct. I try some way but still not found expected result.

Here the snippet code :

const data = [{
      "order-nr": 1,
      "article": "Burger"
    }, {
      "order-nr": 1,
      "article": "Soup"
    }, {
      "order-nr": 1,
      "article": "Noodle"
    }, {
      "order-nr": 2,
      "article": "Steak"
    }, {
      "order-nr": 2,
      "article": "Chicken Wings"
    }, {
      "order-nr": 3,
      "article": "Coffee"
    }, {
      "order-nr": 4,
      "article": "Rice"
    }]

    let tempDataArticle = [];
    let dataArticle = [];
    let orderNr = 1;
    let indexOrderNr = 0;

    for (let i = 0; i < data.length; i++) {
      const datarow = data[i];
      dataArticle.push(datarow);

      if (datarow['order-nr'] === orderNr) {
        tempDataArticle[indexOrderNr] = dataArticle;
      } else {
        tempDataArticle[indexOrderNr] = dataArticle;
        orderNr = orderNr + 1;
        dataArticle = [];
        indexOrderNr = indexOrderNr + 1;
      }
    }

    console.log((tempDataArticle));

Output :

  [
    [{
        "article": "Burger",
        "order - nr": 1
    }, {
        "article": "Soup",
        "order - nr": 1
    }, {
        "article": "Noodle",
        "order - nr": 1
    }, {
        "article": "Steak",
        "order - nr": 2
    }],
    [{
        "article": "Chicken Wings",
        "order - nr": 2
    }, {
        "article": "Coffee",
        "order - nr": 3
    }],
    [{
        "article": "Rice",
        "order - nr": 4
    }]
 ]

Here reproduce code.

Expected Result :

[
[{
    "article": "Burger",
    "order - nr": 1
}, {
    "article": "Soup",
    "order - nr": 1
}, {
    "article": "Noodle",
    "order - nr": 1
}],
[{
    "article": "Steak",
    "order - nr": 2
}, {
    "article": "Chicken Wings",
    "order - nr": 2
}],
[{
    "article": "Coffee",
    "order - nr": 3
}],
[{
    "article": "Rice",
    "order - nr": 4
}]
]

My expected result there is 4 Array base on order-nr key. So the total sub Array will depend on order-nr key.

You said the last object in every array is not correct. What is incorrect about them? The only difference I see is that the expected result contains strings — Jasper
– Jasper, Commented Jul 2, 2021 at 7:37
Sorry and please check again my edit. Current result (output), I have 3 sub array. And last object of that sub array is not correct. My expected result there are 4 sub array. The sub array must depend on value of order-nr key. — MrX
– MrX, Commented Jul 2, 2021 at 7:42

Alex Spelt · Accepted Answer · 2021-07-02 07:42:52Z

3

const data = [{
      "order-nr": 1,
      "article": "Burger"
    }, {
      "order-nr": 1,
      "article": "Soup"
    }, {
      "order-nr": 1,
      "article": "Noodle"
    }, {
      "order-nr": 2,
      "article": "Steak"
    }, {
      "order-nr": 2,
      "article": "Chicken Wings"
    }, {
      "order-nr": 3,
      "article": "Coffee"
    }, {
      "order-nr": 4,
      "article": "Rice"
    }]

let tempDataArticle = [];

for (let i = 0; i < data.length; i++) {
   const order = data[i];

    if(!tempDataArticle[order['order-nr'] - 1])
        tempDataArticle[order['order-nr'] - 1] = [];

    tempDataArticle[order['order-nr'] - 1].push(order)
}

console.log(tempDataArticle);

answered Jul 2, 2021 at 7:42

Alex Spelt

635 bronze badges

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

2 Comments

MrX Over a year ago

Thank you for anwser. Something new for me . I didn't know Javascript can do tempDataArticle[order['order-nr'] - 1].push(order) . Usualy I create temporary container to reuse case like this.

Alex Spelt Over a year ago

I'm glad I could help!

nico263nico · Accepted Answer · 2021-07-02 07:41:39Z

2

Multiples problems here :

indexOrderNr = indexOrderNr + 1; was happening after you detected the item from another order, so the first item of an order would be added to the previous order.

You modified tempDataArticle[indexOrderNr] at every iteration, which is bad since you really don't need to and it makes the program do the same thing multiple times.

Since dataArticle.push(datarow); is done at the start of a new iteration, you add an item to an order without even checking from which order this item is from.

Friendly advice, you can save a lot of time by first working your logic on paper and then start to code.

Here is a working code snippet :

const data = [{
      "order-nr": 1,
      "article": "Burger"
    }, {
      "order-nr": 1,
      "article": "Soup"
    }, {
      "order-nr": 1,
      "article": "Noodle"
    }, {
      "order-nr": 2,
      "article": "Steak"
    }, {
      "order-nr": 2,
      "article": "Chicken Wings"
    }, {
      "order-nr": 3,
      "article": "Coffee"
    }, {
      "order-nr": 4,
      "article": "Rice"
    }]

    let tempDataArticle = [];
    let dataArticle = [];
    let orderNr = 1;
    let indexOrderNr = 0;

    for (let i = 0; i < data.length; i++) {
      var datarow = data[i];
      

      if (datarow['order-nr'] === orderNr) {
        dataArticle.push(datarow);
      } else {
        tempDataArticle[indexOrderNr] = dataArticle;
        orderNr = orderNr + 1;
        dataArticle = [];
        dataArticle.push(datarow);
        indexOrderNr = indexOrderNr + 1;
      }
    }
    tempDataArticle[indexOrderNr] = dataArticle;

    console.log((tempDataArticle));

answered Jul 2, 2021 at 7:41

nico263nico

15111 bronze badges

4 Comments

MrX Over a year ago

Thank you for the answer. It's work. But i don't understand assigning tempDataArticle on line tempDataArticle[indexOrderNr] = dataArticle;. Its outside on loop. But dataArticle will replace with new [] if condition doesn't meet

nico263nico Over a year ago

At every iteration, the code checks if an article is from orderNr. If Yes, add that article to dataArticle. If No, then we have all the articles of an order so it put them in tempDataArticle[indexOrderNr]. It then creates and another empty dataArticle, and adds the article from the new order. However, if this is the last order. The articles from the last order are not yet added since they are added only if it detects an article from a different order. So it needs to add the last order after the for loop is done.

nico263nico Over a year ago

However, I would recommend Alex Spelt solution, since it's more robust. With his solution, you can have the articles of every order not in order and it will work.

MrX Over a year ago

I see, I didn't see another assignment from tempDataArticle. I only see in outside loop. Thank you for the explanation. I still use this answer because there are another code inside the loop.

gil · Accepted Answer · 2021-07-02 07:51:08Z

1

how about this solution:

const data = [{
    "order-nr": 1,
    "article": "Burger"
}, {
    "order-nr": 1,
    "article": "Soup"
}, {
    "order-nr": 1,
    "article": "Noodle"
}, {
    "order-nr": 2,
    "article": "Steak"
}, {
    "order-nr": 2,
    "article": "Chicken Wings"
}, {
    "order-nr": 3,
    "article": "Coffee"
}, {
    "order-nr": 4,
    "article": "Rice"
}]    

let newArr = [];

data.forEach(item => {
    if (newArr[item["order-nr"] - 1] === undefined) {
        newArr[item["order-nr"] - 1] = []
    }
    newArr[item["order-nr"] - 1].push(item);
})

console.log(newArr);

edited Jul 2, 2021 at 7:51

answered Jul 2, 2021 at 7:43

gil

2,5731 gold badge23 silver badges31 bronze badges

Collectives™ on Stack Overflow

Logic to create array of array in JavaScript

3 Answers 3

2 Comments

4 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

2 Comments

4 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related