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63 lines
1.7 KiB
63 lines
1.7 KiB
var each = require('./each');
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var upperFirst = require('./upperFirst');
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exports.linear = function(t) {
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return t;
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};
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var pow = Math.pow;
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var sqrt = Math.sqrt;
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var sin = Math.sin;
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var min = Math.min;
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var asin = Math.asin;
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var PI = Math.PI;
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var fns = {
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sine: function(t) {
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return 1 + sin((PI / 2) * t - PI / 2);
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},
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circ: function(t) {
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return 1 - sqrt(1 - t * t);
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},
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elastic: function(t, m) {
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m = m || DEFAULT_ELASTICITY;
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if (t === 0 || t === 1) return t;
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var p = 1 - min(m, 998) / 1000;
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var st = t / 1;
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var st1 = st - 1;
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var s = (p / (2 * PI)) * asin(1);
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return -(pow(2, 10 * st1) * sin(((st1 - s) * (2 * PI)) / p));
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},
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back: function(t) {
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return t * t * (3 * t - 2);
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},
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bounce: function(t) {
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var pow2,
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bounce = 4;
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while (t < ((pow2 = pow(2, --bounce)) - 1) / 11) {}
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return (
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1 / pow(4, 3 - bounce) - 7.5625 * pow((pow2 * 3 - 2) / 22 - t, 2)
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);
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}
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};
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each(['quad', 'cubic', 'quart', 'quint', 'expo'], function(name, i) {
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fns[name] = function(t) {
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return pow(t, i + 2);
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};
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});
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var DEFAULT_ELASTICITY = 400;
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each(fns, function(fn, name) {
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name = upperFirst(name);
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exports['in' + name] = fn;
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exports['out' + name] = function(t, m) {
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return 1 - fn(1 - t, m);
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};
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exports['inOut' + name] = function(t, m) {
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return t < 0.5 ? fn(t * 2, m) / 2 : 1 - fn(t * -2 + 2, m) / 2;
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};
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exports['outIn' + name] = function(t, m) {
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return t < 0.5
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? (1 - fn(1 - 2 * t, m)) / 2
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: (fn(t * 2 - 1, m) + 1) / 2;
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};
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});
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module.exports = exports;
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