flow like the river

BACK_BACK/node_modules/d3-ease/src/back.js

@@ -0,0 +1,37 @@
+var overshoot = 1.70158;
+
+export var backIn = (function custom(s) {
+  s = +s;
+
+  function backIn(t) {
+    return (t = +t) * t * (s * (t - 1) + t);
+  }
+
+  backIn.overshoot = custom;
+
+  return backIn;
+})(overshoot);
+
+export var backOut = (function custom(s) {
+  s = +s;
+
+  function backOut(t) {
+    return --t * t * ((t + 1) * s + t) + 1;
+  }
+
+  backOut.overshoot = custom;
+
+  return backOut;
+})(overshoot);
+
+export var backInOut = (function custom(s) {
+  s = +s;
+
+  function backInOut(t) {
+    return ((t *= 2) < 1 ? t * t * ((s + 1) * t - s) : (t -= 2) * t * ((s + 1) * t + s) + 2) / 2;
+  }
+
+  backInOut.overshoot = custom;
+
+  return backInOut;
+})(overshoot);