This release adopts ES2015 language features such as for-of and drops support for older browsers, including IE. If you need to support pre-ES2015 environments, you should stick with d3-ease 1.x or use a transpiler.

• Fix various easing functions to ensure that ease(0) = 0 and ease(1) = 1. #27

• Adopt exact paths for imports.
• Adopt explicit files when publishing.
• Add sideEffects: false to the package.json.
• Update dependencies.

• Housekeeping.

• Update dependencies.

• Update dependencies.

• Update dependencies.

• Add module entry point to package.json.

• First stable release.

Changes since D3 3.x

D3 3.x used strings, such as “cubic-in-out”, to identify easing methods; these strings could be passed to d3.ease or transition.ease. D3 4.0 uses symbols instead, such as d3.easeCubicInOut. Symbols are simpler and cleaner. They work well with Rollup to produce smaller custom bundles. You can still define your own custom easing function, too, if desired. Here’s the full list of equivalents:

• linear ↦ d3.easeLinear¹
• linear-in ↦ d3.easeLinear¹
• linear-out ↦ d3.easeLinear¹
• linear-in-out ↦ d3.easeLinear¹
• linear-out-in ↦ d3.easeLinear¹
• poly-in ↦ d3.easePolyIn
• poly-out ↦ d3.easePolyOut
• poly-in-out ↦ d3.easePolyInOut
• poly-out-in ↦ REMOVED²
• quad-in ↦ d3.easeQuadIn
• quad-out ↦ d3.easeQuadOut
• quad-in-out ↦ d3.easeQuadInOut
• quad-out-in ↦ REMOVED²
• cubic-in ↦ d3.easeCubicIn
• cubic-out ↦ d3.easeCubicOut
• cubic-in-out ↦ d3.easeCubicInOut
• cubic-out-in ↦ REMOVED²
• sin-in ↦ d3.easeSinIn
• sin-out ↦ d3.easeSinOut
• sin-in-out ↦ d3.easeSinInOut
• sin-out-in ↦ REMOVED²
• exp-in ↦ d3.easeExpIn
• exp-out ↦ d3.easeExpOut
• exp-in-out ↦ d3.easeExpInOut
• exp-out-in ↦ REMOVED²
• circle-in ↦ d3.easeCircleIn
• circle-out ↦ d3.easeCircleOut
• circle-in-out ↦ d3.easeCircleInOut
• circle-out-in ↦ REMOVED²
• elastic-in ↦ d3.easeElasticOut²
• elastic-out ↦ d3.easeElasticIn²
• elastic-in-out ↦ REMOVED²
• elastic-out-in ↦ d3.easeElasticInOut²
• back-in ↦ d3.easeBackIn
• back-out ↦ d3.easeBackOut
• back-in-out ↦ d3.easeBackInOut
• back-out-in ↦ REMOVED²
• bounce-in ↦ d3.easeBounceOut²
• bounce-out ↦ d3.easeBounceIn²
• bounce-in-out ↦ REMOVED²
• bounce-out-in ↦ d3.easeBounceInOut²

¹ The -in, -out and -in-out variants of linear easing are identical, so there’s just d3.easeLinear. ² Elastic and bounce easing were inadvertently reversed in 3.x, so 4.0 eliminates -out-in easing!

For convenience, there are also default aliases for each easing method. For example, d3.easeCubic is an alias for d3.easeCubicInOut. Most default to -in-out; the exceptions are d3.easeBounce and d3.easeElastic, which default to -out.

Rather than pass optional arguments to d3.ease or transition.ease, parameterizable easing functions now have named parameters: poly.exponent, elastic.amplitude, elastic.period and back.overshoot. For example, in D3 3.x you might say:

var e = d3.ease("elastic-out-in", 1.2);

The equivalent in D3 4.0 is:

var e = d3.easeElastic.amplitude(1.2);

Many of the easing functions have been optimized for performance and accuracy. Several bugs have been fixed, as well, such as the interpretation of the overshoot parameter for back easing, and the period parameter for elastic easing. Also, d3-transition now explicitly guarantees that the last tick of the transition happens at exactly t = 1, avoiding floating point errors in some easing functions.

There’s now a nice visual reference and an animated reference to the new easing functions, too!

See CHANGES for all D3 changes since 3.x.

• Export to the global d3 in vanilla environments (d3/d3#2840).

• Revert the ease interface (#13) in favor of simplicity.

• Adopt easing interface (#13).
• Adopt method chaining for specifying optional easing parameters.

• Prefix exported symbols with “ease”.

• Remove non-in aliases (#12).

• Renamed ease(type[, parameters…]) to bind.

• Fix elasticOut and elasticInOut to be consistent with elasticIn.
• Fix interpretation of s parameter in backInOut to be consistent with backIn and backOut.

• Expose easing functions as symbols rather than strings (e.g., cubic instead of "cubic") .

• Define d3-ease module (and d3_ease global), not ease.

• Adjust the package.json definition for npm users.