Find and edit in nested array?

Question

I have a nested array that changes dynamically. I need to check if the array contains an object and then modify the object keeping the rest of the items the same.

Sample:

var input = [
    ['a', 'b'],
    ['c', 'd'],
    ['e', ['f', 'g']],
    ['h', ['i', 'j']]
]

In this nested array, I would like to find f and change it to f-is-found

var result = [
    ['a', 'b'],
    ['c', 'd'],
    ['e', ['f-is-found', 'g']],
    ['h', ['i', 'j']]
]

The problem is that f can change it's location in the array, so I can't use any hard coded ways of accessing the array.

Help is appreciated, thank you

Nick Parsons · Accepted Answer · 2019-07-27 00:56:37Z

2

You can use a recursive approach, by looping through every element in your array (and looping over every inner-array and so on...), and then check whether your current value is equal to f, if it is, you can modify it, otherwise, if the current value is an array, you can again search that array using the same function.

See example below:

const input = [
  ['a', 'b'],
  ['c', 'd'],
  ['e', ['f', 'g']],
  ['h', ['i', 'j']]
];

function findAndChange(search, toadd, arr) {
  arr.forEach((val, i) => {
    if (!Array.isArray(val)) {
      if (val === search) {
        arr[i] = val + toadd;
      }
    } else {
      findAndChange(search, toadd, val);
    }
  });
}

findAndChange('f', '-is-found', input);
console.log(input);

answered Jul 27, 2019 at 0:56

Nick Parsons

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Comments

vincent · Accepted Answer · 2021-01-11 19:32:36Z

Not a big fan of reinventing the wheel. We use object-scan for a lot of our data processing now and it's powerful once you wrap your head around how to use it. Here is how you could answer your questions.

Note that the input is mutated in place. If you expected multiple instances of 'f', you could simply change the abort to false and change the rnt to count to see how many instances were replaces.

// const objectScan = require('object-scan');

const input = [ ['a', 'b'], ['c', 'd'], ['e', ['f', 'g']], ['h', ['i', 'j']] ];

const modify = (searchValue, replaceValue, data) => objectScan(['**'], {
  rtn: 'bool',
  abort: true,
  filterFn: ({ value, parent, property }) => {
    if (value === searchValue) {
      parent[property] = replaceValue;
      return true;
    }
    return false;
  }
})(input);

const r = modify('f', 'f-is-found', input);

console.log(r); // true iff replace was executed
// => true
console.log(input);
/* =>
  [ [ 'a', 'b' ],
    [ 'c', 'd' ],
    [ 'e', [ 'f-is-found', 'g' ] ],
    [ 'h', [ 'i', 'j' ] ] ]
*/

.as-console-wrapper {max-height: 100% !important; top: 0}

<script src="https://bundle.run/[email protected]"></script>

Disclaimer: I'm the author of object-scan

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