JavaScript search Object Array and return index of parent

Question

I have been looking around for a JavaScript method to return the index of a value but I can't seem to find one that works.

I have the following code:

let topics = [
    {
        id: 1,
        name: 'Topic 1',
        children: [
            {
               id: 2,
               name: 'Subtopic 1.1'  <---- Searching for this value
            }
        ]
    }
];

Is there a method to use on the topics variable to search through the entire object array at once for the value of Subtopic 1.1 and then return the parent index, which in this case would be 0.

zcoop98 · Accepted Answer · 2021-07-16 22:53:06Z

There isn't a single function, but you can nest an Array.prototype.find function inside an Array.prototype.findIndex without issue to achieve what you want (findIndex to search through the parents, find to search through the children):

let topics = [{
    id: 1,
    name: 'Topic 1',
    children: [{
      id: 2,
      name: 'Subtopic 1.1'  // <---- Searching for this value
    }]
  },
  {
    id: 2,
    name: 'Topic 6',
    children: [{
      id: 5,
      name: 'Subtopic 1.7'
    }]
  },
  {
    id: 3,
    name: 'Topic 9',
    children: [{
      id: 4,
      name: 'Subtopic 1.192'
    },
    {
      id: 28,
      name: 'Subtopic 999'
    }],
  },
];

function findParentIndex(name) {
  return topics.findIndex(topic => topic.children.find(child => child.name === name));
}

console.log(findParentId("Subtopic 1.192")); // 3
console.log(findParentId("Subtopic 1.1")); // 1
console.log(findParentId("Not in the list")); // -1

Kinglish · Accepted Answer · 2021-07-16 22:30:33Z

0

You can use array.findIndex()

let topics = [{
  id: 1,
  name: 'Topic 1',
  children: [{
      id: 1,name: 'Subtopic 1.2'
    }, {
      id: 4,name: 'Subtopic 1.4'
    }, {
      id: 2, name: 'Subtopic 1.1'
    }]
}];

const findIndexOf = val => {
  return topics[0].children.findIndex(e => e.name.trim() === val.trim())
}

console.log(findIndexOf('Subtopic 1.1'))

answered Jul 16, 2021 at 22:30

Kinglish

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Comments

ᴓᴓᴓ · Accepted Answer · 2021-07-16 22:46:04Z

0

No.

You would iterate through children, then have a nested loop iterating through each index value. If you find a match, the incrementing variable from the parent loop is the index you want.

edit: code example

let topics = [
    {
        id: 1,
        name: 'Topic 1',
        children: [
            {
               id: 2,
               name: 'Subtopic 1.1' 
            },
            {
                id: 2,
                name: 'Subtopic 3.1' 
             },
             {
                id: 2,
                name: 'Subtopic 1.1' 
             },
             {
                id: 2,
                name: 'Subtopic 2.1' 
             },
             {
                id: 2,
                name: 'Subtopic 1.1' 
             }
     
            ]
    }
];


for (let i in topics[0]["children"]) {
        if (topics[0]["children"][i]["name"] == "Subtopic 1.1") {
            console.log(i)
        }
    
}

edited Jul 16, 2021 at 22:46

answered Jul 16, 2021 at 22:30

ᴓᴓᴓ

1,1761 gold badge7 silver badges18 bronze badges

4 Comments

Dylan Cadd Over a year ago

The topics variable is dynamic and can have X amount of children depending on the data retrieved from a database, would your way still work for that kind of functionality?

ᴓᴓᴓ Over a year ago

I've actually got an error in my code, but yea, the logic would work fine for any number of topics if the code was correct.

ᴓᴓᴓ Over a year ago

I've fixed it now, but I think all three answers here are valid.

Dylan Cadd Over a year ago

Thank you for your response !

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