added: in-elastic, out-elastic, in-out-elastic

Author: matthewmueller

Readme.md

@@ -31,6 +31,9 @@
   - inBounce
   - outBounce
   - inOutBounce
+  - inElastic
+  - outElastic
+  - inOutElastic
 
 ## Aliases
 
@@ -61,6 +64,9 @@
   - in-bounce
   - out-bounce
   - in-out-bounce
+  - in-elastic
+  - out-elastic
+  - in-out-elastic
 
 ## Example
 

index.js

@@ -139,6 +139,34 @@ exports.inOutBounce = function(n){
   return exports.outBounce(n * 2 - 1) * .5 + .5;
 };
 
+exports.inElastic = function(n){
+  var s, a = 0.1, p = 0.4;
+  if ( n === 0 ) return 0;
+  if ( n === 1 ) return 1;
+  if ( !a || a < 1 ) { a = 1; s = p / 4; }
+  else s = p * Math.asin( 1 / a ) / ( 2 * Math.PI );
+  return - ( a * Math.pow( 2, 10 * ( n -= 1 ) ) * Math.sin( ( n - s ) * ( 2 * Math.PI ) / p ) );
+};
+
+exports.outElastic = function(n){
+  var s, a = 0.1, p = 0.4;
+  if ( n === 0 ) return 0;
+  if ( n === 1 ) return 1;
+  if ( !a || a < 1 ) { a = 1; s = p / 4; }
+  else s = p * Math.asin( 1 / a ) / ( 2 * Math.PI );
+  return ( a * Math.pow( 2, - 10 * n) * Math.sin( ( n - s ) * ( 2 * Math.PI ) / p ) + 1 );
+};
+
+exports.inOutElastic = function(n){
+  var s, a = 0.1, p = 0.4;
+  if ( n === 0 ) return 0;
+  if ( n === 1 ) return 1;
+  if ( !a || a < 1 ) { a = 1; s = p / 4; }
+  else s = p * Math.asin( 1 / a ) / ( 2 * Math.PI );
+  if ( ( n *= 2 ) < 1 ) return - 0.5 * ( a * Math.pow( 2, 10 * ( n -= 1 ) ) * Math.sin( ( n - s ) * ( 2 * Math.PI ) / p ) );
+  return a * Math.pow( 2, -10 * ( n -= 1 ) ) * Math.sin( ( n - s ) * ( 2 * Math.PI ) / p ) * 0.5 + 1;
+};
+
 // aliases
 
 exports['in-quad'] = exports.inQuad;
@@ -168,3 +196,6 @@ exports['in-out-back'] = exports.inOutBack;
 exports['in-bounce'] = exports.inBounce;
 exports['out-bounce'] = exports.outBounce;
 exports['in-out-bounce'] = exports.inOutBounce;
+exports['in-elastic'] = exports.inElastic;
+exports['out-elastic'] = exports.outElastic;
+exports['in-out-elastic'] = exports.inOutElastic;