JavaScript - weighted arithmetic mean

In this article, we would like to show you how to calculate the weighted arithmetic mean value in JavaScript.

Runnable example:

// ONLINE-RUNNER:browser;

const calculateWeightedAverage = (values, weights) => {
  	if (values.length !== weights.length) {
    	throw new Error('Values and weights arrays must have same size.');
    }
    let a = 0;
  	let b = 0;
  	for (let i = 0; i < values.length; ++i) {
      	const weight = weights[i];
    	a += weight * values[i];
      	b += weight;
    }
    return a / b;
};


// Usage example:

// Let's suppose we have: 4x 3.0, 9x 4.0 and 4x 5.0

const marks = [3.0, 4.0, 5.0];
const counts = [4, 9, 4];

const average = calculateWeightedAverage(marks, counts);

console.log(average);  // 4

See also

1. JavaScript - average value calculation

2. JavaScript - average value calculation using array reduce()

3. JavaScript - moving average

References

1. Weighted arithmetic mean - Wikipedia