Initial commit 🎉

fbshipit-source-id: b6fc29740c6875d2e78953b8a7123890a67930f2
Co-authored-by: Sebastian McKenzie <sebmck@fb.com>
Co-authored-by: John Knox <jknox@fb.com>
Co-authored-by: Emil Sjölander <emilsj@fb.com>
Co-authored-by: Pritesh Nandgaonkar <prit91@fb.com>

src/utils/LowPassFilter.js

@@ -0,0 +1,51 @@
+/**
+ * Copyright 2018-present Facebook.
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ * @format
+ */
+
+export default class LowPassFilter {
+  constructor(smoothing?: number = 0.9) {
+    this.smoothing = smoothing;
+    this.buffer = [];
+    this.bufferMaxSize = 5;
+  }
+
+  bufferMaxSize: number;
+  smoothing: number;
+  buffer: Array<number>;
+
+  hasFullBuffer(): boolean {
+    return this.buffer.length === this.bufferMaxSize;
+  }
+
+  push(value: number): number {
+    let removed: number = 0;
+
+    if (this.hasFullBuffer()) {
+      removed = this.buffer.shift();
+    }
+
+    this.buffer.push(value);
+
+    return removed;
+  }
+
+  next(nextValue: number): number {
+    // push new value to the end, and remove oldest one
+    const removed = this.push(nextValue);
+
+    // smooth value using all values from buffer
+    const result = this.buffer.reduce(this._nextReduce, removed);
+
+    // replace smoothed value
+    this.buffer[this.buffer.length - 1] = result;
+
+    return result;
+  }
+
+  _nextReduce = (last: number, current: number): number => {
+    return this.smoothing * current + (1 - this.smoothing) * last;
+  };
+}