how can I dynamically access indexes in an array?

Question

I have a rootArray with some nested arrays, it could be any depth.

I want to dynamically access a certain inner array, defined by a list of indexes, to push new content there. so for example, if the list of index is

currentFocusedArray = [1,2]

i want to...

rootArray[1][2].push('new content')

dynamically, not hardwired.

Maybe this is a case of the trees not letting me see the forest or maybe I am on a dead end.

I am just making a note taking simple app, with react, very simple yet.

https://codesandbox.io/embed/quirky-gauss-09i1h

Any advice is welcome! Hopefully I didnt waste your time. Thanks in advance.

You can simply put variables instead of 1 and 2 which you can fill dynamically. Not sure if that's what you mean. — Bernhard
– Bernhard, Commented Jun 3, 2019 at 12:10
I think, you are looking for a recursive function to populate and find any value in nested array. — maddy23285
– maddy23285, Commented Jun 3, 2019 at 12:14
I failed with the title. I need to recursively access an inner array. The depth of the array is not fixed. — daifuco
– daifuco, Commented Jun 3, 2019 at 12:30

Amit Chauhan · Accepted Answer · 2019-06-03 12:12:08Z

1

You can write find array to get array based on your focus array. Use array method reduce to find node from an array of indexes

var updateNode = focus.reduce((node,index) => node && node[index], notes);
updateNode && updateNode.push("new content");

answered Jun 3, 2019 at 12:12

Amit Chauhan

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Vencovsky · Accepted Answer · 2019-06-03 12:20:22Z

0

You can make it with a for loop.

let myArray = rootArray
for(let i = 0; i < currentFocusedArray.length; i++){
    myArray = myArray[currentFocusedArray[i]]
}

After this, you will have myArray reference the deep nested value of rootArray.

let rootArray = {
    "1": {
        "2": []
    }
}
 
let currentFocusedArray = [1, 2]
 
let myArray = rootArray
for(let i = 0; i < currentFocusedArray.length; i++){
    myArray = myArray[currentFocusedArray[i]]
}

myArray.push("new content")

console.log(myArray)

edited Jun 3, 2019 at 12:20

answered Jun 3, 2019 at 12:13

Vencovsky

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Comments

Nenad Vracar · Accepted Answer · 2019-06-03 12:36:34Z

0

You could use reduce to create such function that will set nested array element on any level.

const rootArray = []

function set(arr, index, value) {
  index.reduce((r, e, i, a) => {
    if (!r[e]) {
      if (a[i + 1]) r[e] = []
    } else if (!Array.isArray(r[e])) {
      if (a[i + 1]) {
        r[e] = [r[e]]
      }
    }

    if (!a[i + 1]) {
      if (Array.isArray(r)) {
        r[e] = value
      }
    }

    return r[e]
  }, arr)
}

set(rootArray, [1, 2], 'foo');
set(rootArray, [1, 1, 2], 'bar');
set(rootArray, [1, 2, 2], 'baz');


console.log(JSON.stringify(rootArray))

answered Jun 3, 2019 at 12:36

Nenad Vracar

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