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snippets/js/s/weighted-average.md

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+---
+title: Weighted average
+type: snippet
+language: javascript
+tags: [math]
+cover: interior-12
+dateModified: 2020-11-03T21:46:13+02:00
+---
+
+Calculates the weighted average of two or more numbers.
+
+- Use `Array.prototype.reduce()` to create the weighted sum of the values and the sum of the weights.
+- Divide them with each other to get the weighted average.
+
+```js
+const weightedAverage = (nums, weights) => {
+  const [sum, weightSum] = weights.reduce(
+    (acc, w, i) => {
+      acc[0] = acc[0] + nums[i] * w;
+      acc[1] = acc[1] + w;
+      return acc;
+    },
+    [0, 0]
+  );
+  return sum / weightSum;
+};
+```
+
+```js
+weightedAverage([1, 2, 3], [0.6, 0.2, 0.3]); // 1.72727
+```