To find Index of Multidimensional Array in Javascript

this example seems to work well also with IRREGULAR multidimentional array:

function findIndex(valueToSearch, theArray, currentIndex) {
    if (currentIndex == undefined) currentIndex = '';
        if(Array.isArray(theArray)) {
            for (var i = 0; i < theArray.length; i++) {
                if(Array.isArray(theArray[i])) {
                    newIndex = findIndex(valueToSearch, theArray[i], currentIndex + i + ',');
                    if (newIndex) return newIndex;
               } else if (theArray[i] == valueToSearch) {
                   return currentIndex + i;
               }
            }
    } else if (theArray == valueToSearch) {
        return currentIndex + i;
    }
    return false;
}

var a = new Array();
a[0] = new Array(1, 2, 3, 4, 5);
a[1] = 'ciao';
a[2] = new Array(new Array(6,7),new Array(8,9),10);

var specificIndex = findIndex('10', a);

i wrote this speedly so everyone is invited to improve this function!

p.s. now the function returns a STRING value with all indexes separated by comma, you can simply edit it to returns an object

With findIndex() and indexOf() you can do it in 2 lines:

const valueToSearch = "whatever";
let row = yourArray.findIndex((elem)=>elem.includes(valueToSearch));
let column = yourArray[row].indexOf(valueToSearch);

On jsfiddle

function indexOf2d(arr, val) {
    var index = [-1, -1];

    if (!Array.isArray(arr)) {
        return index;
    }

    arr.some(function (sub, posX) {
        if (!Array.isArray(sub)) {
            return false;
        }

        var posY = sub.indexOf(val);

        if (posY !== -1) {
            index[0] = posX;
            index[1] = posY;
            return true;
        }

        return false;
    });

    return index;
}

console.log(indexOf2d(array, 50));

My code does like a PROCV in MS Excel... and identifies the Index searching only in the first column. Maybe help you (or others).

var convertToRoman = function (valueLimitTen) {   
  var convertTable = [  [1, "I"],
                        [2, "II"],
                        [3, "III"],
                        [4, "IV"],
                        [5, "V"],
                        [6, "VI"],
                        [7, "VII"],
                        [8, "VIII"],
                        [9, "IV"],
                        [10, "X"],
                      ];

  var myIndex;  
  for(var i in convertTable){
    if(convertTable[i][0] == valueLimitTen){
      myIndex = i;      
      return convertTable[i][1];      
    }  
  }  
}

console.log(convertToRoman(2)); //Result II
console.log(convertToRoman(10)); //Result X

ES6 has made this considerably easier.

function findIndexOfNestedArray(nestedArray, searchArray) {
  return searchArray.findIndex(item => {
    return item.length === nestedArray.length
    && item.every((a, i) => a === nestedArray[i])
  })
}

There's a very simple way:

[1,2] === [1,2] // > false
JSON.stringify([1,2]) === JSON.stringify([1,2]) // > true

So we could do something like:

arrays.findIndex(array => JSON.stringify(array)  === JSON.stringify(arrayToCompare))

@Pablito Praderio has a good modern solution above. I have wrapped that into an array method for convenience.

Here is a code snippet:

//  An array of characters:
    array = [];
    for(let i=0; i<5; i++) {
        array[i] = [];
        for(let j=0; j<5; j++) {
            array[i][j] = String.fromCharCode(65+i*5+j);
        }
    }

//  Now add the following method:

    array.coords = function(value) {
        let r = this.findIndex(r => r.includes(value));
        let c = this[r].indexOf(value);
        return [r,c];
    };
  
//  Get Index of, say 'Q'

    console.log(array.coords('Q'));
  

I’ve resisted the urge to add this to the Array prototype, but it makes sense to add it to the individual array object. In any case, you probably only want it for a particular array.