Initial commit with the Cubic Bézier solver.

.travis.yml

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+language: node_js
+node_js:
+  - 0.6

index.js

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+
+module.exports = function(x1, y1, x2, y2, n){
+
+	var xs = [0];
+	var ys = [0];
+
+	var x = 0;
+
+	for (var i = 1; i < (n - 1); i++){
+		var u = 1 / n * i,
+			a = Math.pow(1 - u, 2) * 3 * u,
+			b = Math.pow(u, 2) * 3 * (1 - u),
+			c = Math.pow(u, 3);
+		var _x = x1 * a + x2 * b + c;
+		var _y = y1 * a + y2 * b + c;
+		if ((_x - x) > (10 / n)){
+			x = _x;
+			xs.push(_x);
+			ys.push(_y);
+		}
+	}
+
+	xs.push(1);
+	ys.push(1);
+
+	return function(t){
+
+		var left = 0, right = xs.length - 1;
+		while (left <= right){
+			var middle = Math.floor((left + right) / 2);
+			if (xs[middle] == t) break;
+			else if (xs[middle] > t) right = middle - 1;
+			else left = middle + 1;
+		}
+
+		return ys[middle];
+
+	};	
+
+};

package.json

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+{
+	"author": "Arian Stolwijk",
+	"name": "cubic-bezier",
+	"description": "A small cubic bézier timing function",
+	"version": "0.0.1",
+	"main": "index",
+	"repository": {
+		"type": "git",
+		"url": "git://github.com/arian/cubic-bezier.git"
+	},
+	"scripts": {
+		"test": "node test/test.js"
+	},
+	"dependencies": {},
+	"devDependencies": {}
+}

test/test.js

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+
+var bezier = require('../index');
+var assert = require('assert');
+
+var easeIn = bezier(0.42, 0, 1.0, 1.0, 1000);
+var linear = bezier(0, 0, 1, 1, 1000);
+
+assert.equal(0, easeIn(0));
+assert.equal(1, easeIn(1));
+assert.equal(0.2109793, (Math.round(easeIn(0.4) * 1e7) / 1e7));
+assert.equal(0.4371482, (Math.round(easeIn(0.6) * 1e7) / 1e7));
+
+
+assert.equal(0, linear(0));
+assert.equal(1, linear(1));
+assert.equal(0.3898104, (Math.round(linear(0.4) * 1e7) / 1e7));
+assert.equal(0.608722, (Math.round(linear(0.6) * 1e7) / 1e7));
+
+
+console.log('\033[32m✓    Cubic bézier tests passed\033[0m');