flow like the river

VISUALIZACION/node_modules/d3-ease/src/elastic.js

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+import {tpmt} from "./math.js";
+
+var tau = 2 * Math.PI,
+    amplitude = 1,
+    period = 0.3;
+
+export var elasticIn = (function custom(a, p) {
+  var s = Math.asin(1 / (a = Math.max(1, a))) * (p /= tau);
+
+  function elasticIn(t) {
+    return a * tpmt(-(--t)) * Math.sin((s - t) / p);
+  }
+
+  elasticIn.amplitude = function(a) { return custom(a, p * tau); };
+  elasticIn.period = function(p) { return custom(a, p); };
+
+  return elasticIn;
+})(amplitude, period);
+
+export var elasticOut = (function custom(a, p) {
+  var s = Math.asin(1 / (a = Math.max(1, a))) * (p /= tau);
+
+  function elasticOut(t) {
+    return 1 - a * tpmt(t = +t) * Math.sin((t + s) / p);
+  }
+
+  elasticOut.amplitude = function(a) { return custom(a, p * tau); };
+  elasticOut.period = function(p) { return custom(a, p); };
+
+  return elasticOut;
+})(amplitude, period);
+
+export var elasticInOut = (function custom(a, p) {
+  var s = Math.asin(1 / (a = Math.max(1, a))) * (p /= tau);
+
+  function elasticInOut(t) {
+    return ((t = t * 2 - 1) < 0
+        ? a * tpmt(-t) * Math.sin((s - t) / p)
+        : 2 - a * tpmt(t) * Math.sin((s + t) / p)) / 2;
+  }
+
+  elasticInOut.amplitude = function(a) { return custom(a, p * tau); };
+  elasticInOut.period = function(p) { return custom(a, p); };
+
+  return elasticInOut;
+})(amplitude, period);