access nested uncounted arrays in JavaScript

I have nested arrays those the user made. I want a JavaScript code to access for example "g" element in it

var nestedArrays = [
  [a,b,c,d],
  [e,f,[
    g,h
  ]]
];

in this example i can access "g" element using this code

var element = nestedarrays[2][1][1];

BUT if "g" is nested in 100 of arrays i have to write a lot of square brackets as it

var g = nestedArrays[2][3][1][?][?].....[?];

OR i don't know how much "g" is nested

IS there an easy code to get any element in the nested arrays with pure javascript or jquery ???

2 answers

  • answered 2021-10-24 20:02 TAHER El Mehdi

    We all know that array are zero-based.

    In your first Example to access 'g' You need to access:

    • the second position (index [1]) which is ['e','f',['g','h']]
    • then access the third position (index [2]) which is ['g','h']
    • finally the first position (index [0]) and you get 'g'.
    var nestedArrays = [['a','b','c','d'],['e','f',['g','h']]];
    let x = nestedArrays[1][2][0];
    console.log(x); // g
    

    So from that we can say that to access 'g'
    We need to follow this road of indices [1,2,0]

    var nestedArrays = [['a','b','c','d'],['e','f',['g','h']]];
    let roadToG = [1,2,0];
    
    for(let i = 0; i < roadToG.length; i++){
        nestedArrays = nestedArrays[roadToG[i]];
    }
    console.log(nestedArrays); // g
    

    BUT if "g" is nested in 100 of arrays i have to write a lot of square brackets as it var g = nestedArrays[2][3][1][?][?].....[?];

    In case we want to access 'g' dynamically without hard code the road of indices; We must loop recursively in array till we find 'g', in looping we keep track of road

    function loopRecursively( arr, x ,roadToX = []){
        if(JSON.stringify(arr).indexOf(x) == -1) return null; //in edge case where there is no x in array; we just return null!
        for ( let i = 0; i < arr.length; i++ ) {
            if( arr[i] == x ){
                roadToX.push(i);
            } else if( Array.isArray( arr[i] ) && JSON.stringify(arr[i]).indexOf(x) != -1 ){
                roadToX.push(i);
                loopRecursively( arr[i] , x, roadToX);
            }
        }
        return roadToX;
    }
    let nestedArrays = [['a','b','c','d'],['e','f',['g','h']]];
    console.log( loopRecursively( nestedArrays, 'g' ) ); // [1, 2, 0]
    

  • answered 2021-10-24 20:12 ray hatfield

    If you're just trying to find a particular element you could flatten the array and find it that way.

    var nestedArrays = [
      ['a','b','c','d'],
      ['e','f',[
        'g','h'
      ]]
    ];
    
    const g = nestedArrays.flat(Infinity).find(x => x === 'g');
    
    console.log(g);

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