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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 ???

Mohamed Maher
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  • Sure, depending on what "g" is, and how you decide to define "equality". It's a recursive find operation. – Dave Newton Oct 24 '21 at 18:19
  • Recursion. This should give you all the information you need: [How can I access and process nested objects, arrays or JSON?](https://stackoverflow.com/questions/11922383/how-can-i-access-and-process-nested-objects-arrays-or-json) (whether that's "easy" or not is for you to decide). – Felix Kling Oct 24 '21 at 18:19

2 Answers2

0
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]
XMehdi01
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  • I want an element that's deep in the nestedarray I tried the second code you have written in console and it worked but in my code it displays this error >> Uncaught SyntaxError: Unexpected end of input – Mohamed Maher Oct 26 '21 at 06:26
0

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);
ray
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