Convert number to a reversed array of digits in JavaScript

Given a non-negative integer, we need to write a function that returns an array containing the digits in reverse order. This is a common programming challenge that demonstrates string manipulation and array operations.

Example

348597 => The correct solution should be [7,9,5,8,4,3]

Method 1: Using String Split and Reverse

The most straightforward approach is to convert the number to a string, split it into individual characters, reverse the array, and convert back to numbers:

const num = 348597;

const reverseArrify = num => {
    return String(num).split('').reverse().map(digit => Number(digit));
};

console.log(reverseArrify(num));
console.log(reverseArrify(12345));
console.log(reverseArrify(0));

[ 7, 9, 5, 8, 4, 3 ]
[ 5, 4, 3, 2, 1 ]
[ 0 ]

Method 2: Using Mathematical Operations

We can also solve this without string conversion by using modulo and division operations:

const reverseArrifyMath = num => {
    const result = [];
    while (num > 0) {
        result.push(num % 10);
        num = Math.floor(num / 10);
    }
    return num === 0 && result.length === 0 ? [0] : result;
};

console.log(reverseArrifyMath(348597));
console.log(reverseArrifyMath(12345));
console.log(reverseArrifyMath(0));

[ 7, 9, 5, 8, 4, 3 ]
[ 5, 4, 3, 2, 1 ]
[ 0 ]

Method 3: Using Spread Operator

A more concise approach using the spread operator:

const reverseArrifySpread = num => {
    return [...String(num)].reverse().map(Number);
};

console.log(reverseArrifySpread(348597));
console.log(reverseArrifySpread(789));

[ 7, 9, 5, 8, 4, 3 ]
[ 9, 8, 7 ]

Comparison

Key Points

• All methods handle single-digit numbers and zero correctly
• String-based approaches are more readable but involve type conversion
• Mathematical approach avoids string conversion but requires more code
• The spread operator provides the most concise solution

Conclusion

Converting numbers to reversed digit arrays can be achieved through multiple approaches. The string split and reverse method offers the best balance of readability and performance for most use cases.