Convert nested array to string - JavaScript

Converting a nested array to a string in JavaScript involves flattening all nested elements and concatenating their values. This is commonly needed when processing complex data structures.

Problem Statement

We need to write a JavaScript function that takes a nested array of literals and converts it to a single string by concatenating all values, regardless of nesting depth.

const arr = [
    'hello', [
        'world', 'how', [
            'are', 'you', [
                'without', 'me'
            ]
        ]
    ]
];

Method 1: Using Recursive Function

The most straightforward approach is to use recursion to traverse each level of nesting:

const arr = [
    'hello', [
        'world', 'how', [
            'are', 'you', [
                'without', 'me'
            ]
        ]
    ]
];

const arrayToString = (arr) => {
    let str = '';
    for(let i = 0; i 

helloworldhowareyouwithoutme


Method 2: Using Array.flat() and join()

A more modern approach uses the built-in flat() method with infinite depth:

const arr = [
    'hello', [
        'world', 'how', [
            'are', 'you', [
                'without', 'me'
            ]
        ]
    ]
];

const arrayToString = (arr) => {
    return arr.flat(Infinity).join('');
};

console.log(arrayToString(arr));


helloworldhowareyouwithoutme


Method 3: Using toString() Method

JavaScript's built-in toString() method also flattens arrays, though it adds commas by default:

const arr = [
    'hello', [
        'world', 'how', [
            'are', 'you', [
                'without', 'me'
            ]
        ]
    ]
];

const arrayToString = (arr) => {
    return arr.toString().replace(/,/g, '');
};

console.log(arrayToString(arr));


helloworldhowareyouwithoutme


Comparison

Conclusion

For modern applications, use Array.flat(Infinity).join('') as it's the most concise and performant. For legacy browser support, the recursive approach provides reliable cross-browser compatibility.