JavaScript to check consecutive numbers in array?

To check for consecutive numbers in an array, you can use JavaScript's reduce() method or simpler approaches. This returns true for consecutive sequences like 100, 101, 102, and false otherwise.

Method 1: Using reduce() with Objects

This approach works with arrays of objects containing number properties:

const sequenceIsConsecutive = (obj) =>
    Boolean(obj.reduce((output, latest) => (output ?
        (Number(output.number) + 1 === Number(latest.number) ? latest : false)
        : false)));

console.log("Is Consecutive = " + sequenceIsConsecutive([
    { number: '100' },
    { number: '101' },
    { number: '102' }
]));

console.log("Is Consecutive = " + sequenceIsConsecutive([
    { number: '100' },
    { number: '102' },
    { number: '104' }
]));

Is Consecutive = true
Is Consecutive = false

Method 2: Simple Array of Numbers

For basic arrays of numbers, this simpler approach is more readable:

function isConsecutive(arr) {
    if (arr.length 

Is Consecutive = true
Is Consecutive = false
Is Consecutive = true


Method 3: Using every() Method

The every() method provides another clean solution:

function checkConsecutive(arr) {
    return arr.every((num, index) => 
        index === 0 || num === arr[index - 1] + 1
    );
}

console.log("Is Consecutive = " + checkConsecutive([1, 2, 3, 4]));
console.log("Is Consecutive = " + checkConsecutive([10, 12, 14]));
console.log("Is Consecutive = " + checkConsecutive([50, 51, 52, 53]));


Is Consecutive = true
Is Consecutive = false
Is Consecutive = true


Comparison

Conclusion

Use the simple loop approach for basic number arrays, or every() for a functional programming style. The reduce() method works well with complex object structures.