Class as a set of methods in OOP in JavaScript

Sometimes classes are used to group methods of similar topics. In this case, as a rule, only one object of this class is created and its methods are used many times in different situations.

Let's look at an example. Let's make a class that will manipulate arrays of numbers:

javascriptclass ArrHelper {
  
}

Each method of this class will take an array as a parameter and perform a given operation on it. Let's say, for example, we have the following methods:

javascriptclass ArrHelper {
  getSum(arr) {
    // sum of elements
  }
  
  getAvg(arr) {
    // arithmetic mean arithmetical mean mean
  }
}

Let's write the implementation of these methods:

javascriptclass ArrHelper {
  getSum(arr) {
    let res = 0;
    
    for (let num of arr) {
      res += num;
    }
    
    return res;
  }
  
  getAvg(arr) {
    if (arr.length > 0) {
      let sum = this.getSum(arr);
      return sum / arr.length;
    } else {
      return 0;
    }
  }
}

Let's see how we will use these methods. Let's create an object of our class:

javascriptlet arrHelper = new ArrHelper;

Let's find the sum of numbers in different arrays using our object:

javascriptlet sum1 = arrHelper.getSum([1, 2, 3]);
console.log(sum1);

let sum2 = arrHelper.getSum([3, 4, 5]);
console.log(sum2);