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How to generate child keys by parent keys in array JavaScript?
Let’s say, we have an array of objects like this −
const arr = [
{ id: 1, parent_id: 0, title: 'Movies' },
{ id: 2, parent_id: 0, title: 'Music' },
{ id: 3, parent_id: 1, title: 'Russian movies' },
{ id: 4, parent_id: 2, title: 'Russian music' },
{ id: 5, parent_id: 3, title: 'New' },
{ id: 6, parent_id: 3, title: 'Top10' },
{ id: 7, parent_id: 4, title: 'New' },
{ id: 8, parent_id: 4, title: 'Top10' },
{ id: 9, parent_id: 0, title: 'Soft' }
];We are required to write a function that takes in this array and returns a new array of object with each object having an extra property “child” which must be an array of all the ids of object which are direct or indirect child of a particular object.
Therefore, the output should look like −
[
{ id: 1, parent_id: 0, title: 'Movies', childs: [ 3, 5, 6 ] },
{ id: 2, parent_id: 0, title: 'Music', childs: [ 4, 7, 8 ] },
{ id: 3, parent_id: 1, title: 'Russian movies', childs: [ 5, 6 ] },
{ id: 4, parent_id: 2, title: 'Russian music', childs: [ 7, 8 ] },
{ id: 5, parent_id: 3, title: 'New', childs: [] },
{ id: 6, parent_id: 3, title: 'Top10', childs: [] },
{ id: 7, parent_id: 4, title: 'New', childs: [] },
{ id: 8, parent_id: 4, title: 'Top10', childs: [] },
{ id: 9, parent_id: 0, title: 'Soft', childs: [] }
]Now, let’s write the code for this function −
Example
const arr = [
{ id: 1, parent_id: 0, title: 'Movies' },
{ id: 2, parent_id: 0, title: 'Music' },
{ id: 3, parent_id: 1, title: 'Russian movies' },
{ id: 4, parent_id: 2, title: 'Russian music' },
{ id: 5, parent_id: 3, title: 'New' },
{ id: 6, parent_id: 3, title: 'Top10' },
{ id: 7, parent_id: 4, title: 'New' },
{ id: 8, parent_id: 4, title: 'Top10' },
{ id: 9, parent_id: 0, title: 'Soft' }
];
const generateChild = arr => {
return arr.reduce((acc, val, ind, array) => {
const childs = [];
array.forEach((el, i) => {
if(childs.includes(el.parent_id) || el.parent_id === val.id){
childs.push(el.id);
};
});
return acc.concat({...val, childs});
}, []);
};
console.log(generateChild(arr));Output
The output in the console will be −
[
{ id: 1, parent_id: 0, title: 'Movies', childs: [ 3, 5, 6 ] },
{ id: 2, parent_id: 0, title: 'Music', childs: [ 4, 7, 8 ] },
{ id: 3, parent_id: 1, title: 'Russian movies', childs: [ 5, 6 ] },
{ id: 4, parent_id: 2, title: 'Russian music', childs: [ 7, 8 ] },
{ id: 5, parent_id: 3, title: 'New', childs: [] },
{ id: 6, parent_id: 3, title: 'Top10', childs: [] },
{ id: 7, parent_id: 4, title: 'New', childs: [] },
{ id: 8, parent_id: 4, title: 'Top10', childs: [] },
{ id: 9, parent_id: 0, title: 'Soft', childs: [] }
]
Updated on: 26-Aug-2020
2K+ Views
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