unitbezier

Unit bezier interpolation function: a port to JavaScript from Webkit:

http://svn.webkit.org/repository/webkit/trunk/Source/WebCore/platform/graphics/UnitBezier.h

API

import unitBezier from '@mapbox/unitbezier';

const ease = unitBezier(0.25, 0.1, 0.25, 1); // CSS `ease`
ease(0.5);        // → 0.8024…
ease(0.5, 1e-8);  // tighter precision

unitBezier(p1x, p1y, p2x, p2y)

Returns a function that evaluates the cubic bezier curve defined by control points (0,0), (p1x, p1y), (p2x, p2y), (1,1).

ease(x, epsilon?)

Evaluate the curve for x (clamped to [0, 1]). epsilon controls solver precision (default 1e-6).