easing functions

1 files changed, 29 insertions, 0 deletions

diff --git a/js/util.js b/js/util.js
index 911e44b..f76fc8e 100644
--- a/js/util.js
+++ b/js/util.js
@@ -114,3 +114,32 @@ function weave(a){
   reverse(aa[1]).forEach(function(el){ b.push(el) })
   return b
 }
+
+// easing functions
+function circular (t) { return Math.sqrt( 1 - ( --t * t ) ) }
+function quadratic (t) { return t * ( 2 - t ) }
+function back (t) {
+  var b = 4;
+  return ( t = t - 1 ) * t * ( ( b + 1 ) * t + b ) + 1;
+}
+function bounce (t) {
+  if (t >= 1) return 1;
+  if ( ( t /= 1 ) < ( 1 / 2.75 ) ) {
+    return 7.5625 * t * t;
+  } else if ( t < ( 2 / 2.75 ) ) {
+    return 7.5625 * ( t -= ( 1.5 / 2.75 ) ) * t + 0.75;
+  } else if ( t < ( 2.5 / 2.75 ) ) {
+    return 7.5625 * ( t -= ( 2.25 / 2.75 ) ) * t + 0.9375;
+  } else {
+    return 7.5625 * ( t -= ( 2.625 / 2.75 ) ) * t + 0.984375;
+  }
+}
+function elastic (t) {
+  var f = 0.22,
+      e = 0.4;
+
+  if ( t === 0 ) { return 0; }
+  if ( t == 1 ) { return 1; }
+
+  return ( e * Math.pow( 2, - 10 * t ) * Math.sin( ( t - f / 4 ) * ( 2 * Math.PI ) / f ) + 1 );
+}