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

JavaScript Basic: Exercise-122 with Solution

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

Pictorial Presentation:

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

Sample Solution:

HTML Code:

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title> Check whether a given array of integers represents either a strictly increasing or a strictly decreasing sequence</title>
</head>
<body>

</body>
</html>

JavaScript Code:

function is_monotonous(num) {
    if (num.length === 1) {
        return true;
    }
    var num_direction = num[1] - num[0];
    for (var i = 0; i < num.length - 1; i++) {
        if (num_direction * (num[i + 1] - num[i]) <= 0) {
            return false;
        }
    }
    return true;
}
console.log(is_monotonous([1, 2, 3]));
console.log(is_monotonous([1, 2, 2]))
console.log(is_monotonous([-3, -2, -1]))

Sample Output:

true
false
true

Flowchart:

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

ES6 Version:

function is_monotonous(num) {
    if (num.length === 1) {
        return true;
    }
    const num_direction = num[1] - num[0];
    for (let i = 0; i < num.length - 1; i++) {
        if (num_direction * (num[i + 1] - num[i]) <= 0) {
            return false;
        }
    }
    return true;
}
console.log(is_monotonous([1, 2, 3]));
console.log(is_monotonous([1, 2, 2]))
console.log(is_monotonous([-3, -2, -1]))

Live Demo:

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


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Previous: Write a JavaScript program to check if a given matrix is lower triangular or not.
Next: Write a JavaScript program to find if the members of an given array of integers is a permutation of numbers from 1 to a given integer.

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JavaScript: Tips of the Day

Returns the sum of the powers of all the numbers from start to end (both inclusive)

Example:

const sumPower = (end, power = 2, start = 1) =>
  Array(end + 1 - start)
    .fill(0)
    .map((x, i) => (i + start) ** power)
    .reduce((a, b) => a + b, 0);
console.log(sumPower(10)); // 385
console.log(sumPower(10, 3)); // 3025
console.log(sumPower(10, 3, 5)); // 2925 

Output:

385
3025
2925