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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

Parameter's value

function getItems(fruitList, ...args, favoriteFruit) {
  return [...fruitList, ...args, favoriteFruit]
}

getItems(["banana", "apple"], "pear", "orange")

...args is a rest parameter. The rest parameter's value is an array containing all remaining arguments, and can only be the last parameter! In this example, the rest parameter was the second parameter. This is not possible, and will throw a syntax error.

function getItems(fruitList, favoriteFruit, ...args) {
  return [...fruitList, ...args, favoriteFruit];
}


getItems(['banana', 'apple'], 'pear', 'orange');
The above example works. This returns the array [ 'banana', 'apple', 'orange', 'pear' ].

Ref: https://bit.ly/3jFRBje