# JavaScript program to find the nearest number in an array

## Nearest number in an array :

Our problem is to find the nearest number in an array specific to a *given* number. For example, if our array is *[1,5,10,15,20]* and if the given number is *18*, the output of the program should be *20* as this is the nearest number to *18* in this array. Again, if the number is *16*, it will print *15*. Note that we are checking in both ways to find the nearest number.

I will show you different ways to solve this. For each program, the *array* and the *number* is already given. The *JavaScript* program will find the nearest member and print that out. The main part is written in a separate function for each case.

## Method 1 : Using a loop :

- This is a
*straight forward*way to find out the nearest number. In simple words :

Use one variable to store the current closest number. Assign its value to the first element of the array. We will keep updating it and it will hold the final result value at the end of the program. - Run one
*for loop*to iterate through the numbers one by one. - For each number, find its difference to the given number. Find if it is less than the difference of the given number and current
*closest*or not. If yes, assign it as the*closest*. - Keep updating the
*closest*variable with the loop and return it at the end of the program.

Below is the complete *JavaScript* program :

const findClosest = (arr,num) => { if(arr == null) { return } let closest = arr[0]; for(let item of arr){ if(Math.abs(item - num)<Math.abs(closest - num)){ closest = item; } } return closest; } const array = [10,20,30,40,50,60,70,80,90]; const num = 36; console.log(findClosest(array,num));

### Explanation :

- Here,
*findClosest*function is used to find the closest number in an array with respect to a given number. It takes two parameters :*arr*is the array with all numbers and*num*is the given number. - If the provided array is
*null*, return. *closest*variable will hold the nearest value to*num*. Initialize it with the first element of the array.- Run one
*for-of*loop to iterate through the elements of the array. - For each element, check the absolute difference of
*current element, given number*and*current closest, given number*. Update the value of*closest*based on this comparison. - Finally, return the
*closest*number found.

## Method 2 : Using reduce :

*reduce* function calculates one result from a *JavaScript* array. It takes one function and use it to find the final result. We can use *reduce* to find out the closest element to a given value in an array. Below is the complete program :

const findClosest = (arr,num) => { if(arr == null){ return } return arr.reduce((prev,current) => Math.abs(current - num)<Math.abs(prev - num) ? current : prev); } const array = [10,20,30,40,50,60,70,80,90]; const num = 36; console.log(findClosest(array,num));

### Explanation :

We are using same function name *findClosest* as the previous example. It take one *array* and the *number* as arguments and returns the closest member found relative to the given number.

- The main concept of this solution is same as the previous example. It calculates the
*absolute*difference of the previous and current number with respect to the given number and returns the closest value. - At the end, it results the closest number with respect to the given number.

## Method 3: Using sort :

In *JavaScript*, sorting can be done in many ways. Not only increasing and decreasing. You can define the *rule* how you want to sort. We can write our program to sort the array such that the number that is closest to the given number moves to the end of the array as like below :

const findClosest = (arr,num) => { if(array == null){ return } return arr.sort((a,b) => Math.abs(b - num) - Math.abs(a-num)).pop(); } const array = [10,20,30,40,50,60,70,80,90]; const num = 36; console.log(findClosest(array,num));

### Explanation :

Here, we are sorting the array in such a way that the number that is closest to the given number moves to the end of the array. The final array after *sorting* in the above example will be *[ 90, 80, 70, 10, 60, 20, 50, 30, 40 ]*. Next, we are using *pop()* to remove the last element.

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