JavaScript: Check whether a given array of integers represents either a strictly increasing or a strictly decreasing sequence

JavaScript Basic: Exercise-122 with Solution

Check if Array is Strictly Increasing/Decreasing

Write a JavaScript program to check whether a given array of integers represents a strictly increasing or decreasing sequence.

Visual Presentation:

Sample Solution:

JavaScript Code:

// Function to check if a sequence of numbers is monotonous
function is_monotonous(num) {
    // If the sequence has only one element, it's considered monotonous
    if (num.length === 1) {
        return true;
    }

    // Calculate the direction of the sequence
    var num_direction = num[1] - num[0];

    // Check for non-monotonic behavior
    for (var i = 0; i < num.length - 1; i++) {
        // If the product of direction and the difference between elements is not positive, it's non-monotonic
        if (num_direction * (num[i + 1] - num[i]) <= 0) {
            return false;
        }
    }
    // If the loop completes, the sequence is monotonic
    return true;
}

// Test cases
console.log(is_monotonous([1, 2, 3]));    // Output: true (Monotonously increasing)
console.log(is_monotonous([1, 2, 2]));    // Output: false (Not strictly increasing)
console.log(is_monotonous([-3, -2, -1])); // Output: true (Monotonously increasing) 

Output:

true
false
true

Live Demo:

See the Pen javascript-basic-exercise-122 by w3resource (@w3resource) on CodePen.

Flowchart:

ES6 Version:

// Function to check if a sequence of numbers is monotonous
const is_monotonous = (num) => {
    // If the sequence has only one element, it's considered monotonous
    if (num.length === 1) {
        return true;
    }

    // Calculate the direction of the sequence
    const num_direction = num[1] - num[0];

    // Check for non-monotonic behavior
    for (let i = 0; i < num.length - 1; i++) {
        // If the product of direction and the difference between elements is not positive, it's non-monotonic
        if (num_direction * (num[i + 1] - num[i]) <= 0) {
            return false;
        }
    }
    // If the loop completes, the sequence is monotonic
    return true;
};

// Test cases
console.log(is_monotonous([1, 2, 3]));    // Output: true (Monotonously increasing)
console.log(is_monotonous([1, 2, 2]));    // Output: false (Not strictly increasing)
console.log(is_monotonous([-3, -2, -1])); // Output: true (Monotonously increasing)

For more Practice: Solve these Related Problems:

• Write a JavaScript program that checks if an array of integers is strictly increasing by comparing each element with its predecessor.
• Write a JavaScript function that determines whether an array is strictly increasing or strictly decreasing without altering the original order.
• Write a JavaScript program that returns a descriptive message indicating if an array is strictly increasing, strictly decreasing, or neither.

Go to:

• JavaScript basic Exercises Home ↩
• JavaScript Exercises Home ↩

PREV : Check if Matrix is Lower Triangular.
NEXT : Check if Array is Permutation of Numbers 1 to n.

Improve this sample solution and post your code through Disqus.