Easy Ease

A tiny easing package (~0.2 KB gzipped) with no dependencies. For doing stuff like:

• Scrolling smoothly to the top of the page
• Sliding out a navigation menu
• Sliding open an accordion component

You won't find any options for different types of easing here. What you get is a nice ease-in-out similar to the default animation for transition in CSS.

If you'd prefer to choose from the full suite of Robert Penner equations, try tween.js or d3-ease instead.

Usage

npm install easy-ease

Example

To scroll the window to the top of the page:

import ease from 'easy-ease';

ease({
  startValue: window.scrollY,
  endValue: 0,
  onStep: value => window.scroll(0, value),
});

Have a play with some other examples on CodePen https://codepen.io/davidgilbertson/pen/GyrZNz

API

The ease function takes a single parameter, an object. The properties of that object are:

Property	Type	Description	Default
startValue	Number	The value at which to start	0
endValue	Number	The value at which to end	1
durationMs	Number	The amount of time (in milliseconds) the transition should take	200
onStep	Function	This will be called on each step of the transition. That's once for each 'animation frame' - roughly every 16 milliseconds. The current value is passed as the only argument. The last time it is called the value is guaranteed to be endValue.	No default
onComplete	Function	Called when the transition is complete. Will be called after the final call to onStep. No argument is passed to this function.	noop