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JavaScript: Return 1 if the array is sorted in ascending order, -1 if it is sorted in descending order or 0 if it is not sorted

JavaScript fundamental (ES6 Syntax): Exercise-188 with Solution

Write a JavaScript program that will return 1 if the array is sorted in ascending order, -1 if it is sorted in descending order or 0 if it is not sorted.

  • Calculate the ordering direction for the first pair of adjacent array elements.
  • Return 0 if the given array is empty, only has one element or the direction changes for any pair of adjacent array elements.
  • Use Math.sign() to covert the final value of direction to -1 (descending order) or 1 (ascending order).

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2 
const isSorted = arr => {
  let direction = -(arr[0] - arr[1]);
  for (let [i, val] of arr.entries()) {
    direction = !direction ? -(arr[i - 1] - arr[i]) : direction;
    if (i === arr.length - 1) return !direction ? 0 : direction;
    else if ((val - arr[i + 1]) * direction > 0) return 0;
  }
};
console.log(isSorted([0, 1, 2, 2]));
console.log(isSorted([4, 3, 2]));
console.log(isSorted([4, 3, 5]));

Sample Output:

1
-1
0

Pictorial Presentation:

JavaScript Fundamental: Return 1 if the array is sorted in ascending order, -1 if it is sorted in descending order or 0 if it is not sorted.
JavaScript Fundamental: Return 1 if the array is sorted in ascending order, -1 if it is sorted in descending order or 0 if it is not sorted.
JavaScript Fundamental: Return 1 if the array is sorted in ascending order, -1 if it is sorted in descending order or 0 if it is not sorted.

Flowchart:

flowchart: Return 1 if the array is sorted in ascending order, -1 if it is sorted in descending order or 0 if it is not sorted

Live Demo:

See the Pen javascript-basic-exercise-188-1 by w3resource (@w3resource) on CodePen.


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JavaScript: Tips of the Day

How to check whether a string contains a substring in JavaScript?

ECMAScript 6 introduced String.prototype.includes:

const string = "foo";
const substring = "oo";

console.log(string.includes(substring));

includes doesn't have Internet Explorer support, though. In ECMAScript 5 or older environments, use String.prototype.indexOf, which returns -1 when a substring cannot be found: 

var string = "foo";
var substring = "oo";

console.log(string.indexOf(substring) !== -1);

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