# Finding the inclination of arrays in JavaScript

We are required to write a JavaScript function that takes in an array of numbers and returns true if it’s either strictly increasing or strictly decreasing, otherwise returns false.

In Mathematics, a strictly increasing function is that function in which the value to be plotted always increases. Similarly, a strictly decreasing function is that function in which the value to be plotted always decreases.

Therefore, let’s write the code for this function −

## Example

The code for this will be −

const arr = [12, 45, 6, 4, 23, 23, 21, 1];
const arr2 = [12, 45, 67, 89, 123, 144, 2656, 5657];
const sameSlope = (a, b, c) => (b - a < 0 && c - b < 0) || (b - a > 0 && c - b > 0);
const increasingOrDecreasing = (arr = []) => {
if(arr.length <= 2){
return true;
};
for(let i = 1; i < arr.length - 1; i++){
if(sameSlope(arr[i-1], arr[i], arr[i+1])){
continue;
};
return false;
};
return true;
};
console.log(increasingOrDecreasing(arr));
console.log(increasingOrDecreasing(arr2));

## Output

The output in the console will be −

false
true