Question 160396 in Javascript Question posted in
A very good W3school tutorial can be found here.

How do you access the nth element of a nested array in JavaScript?

Consider the following JS array:

let text = [
{
  line: [{
    words: [{
      word: [
        { letter: 'H' },
        { letter: 'i' },
        { letter: ' ' },
      ],
    },
    {
      word: [
        { letter: 'J' },
        { letter: 'i' },
        { letter: 'm' },
        { letter: 'n' },
      ],
    }],
  }]
},
{
  line: [{
    words: [{
      word: [
        { letter: 'H' },
        { letter: 'i' },
        { letter: ' ' },
      ],
    },
    {
      word: [
        { letter: 'J' },
        { letter: 'o' },
        { letter: 'n' },
      ],
    }],
  }]
}

]

Is there a fast (and simple) way to access the nth letter?
For example :

  • if n=0, get ‘H’
  • if n=1, get ‘i’
  • …
  • if n=11, get ‘o’

Here is a JSFiddle: https://jsfiddle.net/Imabot/6usdej75/

Tags:

2

Answers


  1. 0

    I solved it with flat and flatMap:

    let text = [
  {
    line: [{
      words: [{
        word: [
          { letter: 'H' },
          { letter: 'i' },
          { letter: ' ' },
        ],
      },
      {
        word: [
          { letter: 'J' },
          { letter: 'i' },
          { letter: 'm' },
          { letter: 'n' },
        ],
      }],
    }]
  },
  {
    line: [{
      words: [{
        word: [
          { letter: 'H' },
          { letter: 'i' },
          { letter: ' ' },
        ],
      },
      {
        word: [
          { letter: 'J' },
          { letter: 'o' },
          { letter: 'n' },
        ],
      }],
    }]
  }
];

const flat = text.map(({ line }) => line.map(({ words }) => words.map(({ word }) => word)).flatMap(item => item.flat())).flat();
function getIndex(array, index) {
  return array[index];
}
console.log(getIndex(flat, 0));
console.log(getIndex(flat, 1));
console.log(getIndex(flat, 11));
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  2. 0

    I think a good option is to use any loop to break it at the index you need:

    let text = [
{
  line: [{
    words: [{
      word: [
        { letter: 'H' },
        { letter: 'i' },
        { letter: ' ' },
      ],
    },
    {
      word: [
        { letter: 'J' },
        { letter: 'i' },
        { letter: 'm' },
        { letter: 'n' },
      ],
    }],
  }]
},
{
  line: [{
    words: [{
      word: [
        { letter: 'H' },
        { letter: 'i' },
        { letter: ' ' },
      ],
    },
    {
      word: [
        { letter: 'J' },
        { letter: 'o' },
        { letter: 'n' },
      ],
    }],
  }]
}
];

console.log( findLetter(text, 0) );
console.log( findLetter(text, 1) );
console.log( findLetter(text, 11) );

function findLetter(text = [], index = 0) {
  let i = 0;
  for (let {line} of text) {
    for (let {words} of line) {
      for (let {word} of words) {
        if (word.length + i <= index) {
          i += word.length;
        } else {
          return word[index - i].letter;
        }
      }
    }
  }
}
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