Rename js snippets

snippets/js/s/sum-powers-in-range.md

@@ -0,0 +1,29 @@
+---
+title: Sum of powers in range
+type: snippet
+language: javascript
+tags: [math]
+cover: boat-port
+dateModified: 2020-10-22T20:24:30+03:00
+---
+
+Calculates the sum of the powers of all the numbers from `start` to `end` (both inclusive).
+
+- Use `Array.prototype.fill()` to create an array of all the numbers in the target range.
+- Use `Array.prototype.map()` and the exponent operator (`**`) to raise them to `power` and `Array.prototype.reduce()` to add them together.
+- Omit the second argument, `power`, to use a default power of `2`.
+- Omit the third argument, `start`, to use a default starting value of `1`.
+
+```js
+const sumPower = (end, power = 2, start = 1) =>
+  Array(end + 1 - start)
+    .fill(0)
+    .map((x, i) => (i + start) ** power)
+    .reduce((a, b) => a + b, 0);
+```
+
+```js
+sumPower(10); // 385
+sumPower(10, 3); // 3025
+sumPower(10, 3, 5); // 2925
+```