# spring-easing [![Open Bundle](https://bundlejs.com/badge-light.svg)](https://bundlejs.com/?q=spring-easing&bundle "Check the total bundle size of spring-easing with whichever animation library you choose.") [NPM](https://www.npmjs.com/package/spring-easing) | [Deno](https://deno.land/x/spring_easing) | [GitHub](https://github.com/okikio/spring-easing#readme) | [Docs](https://spring-easing.okikio.dev) | [License](#license) Quick and easy spring animations. Works with other animation libraries ([gsap](https://greensock.com/), [animejs](https://animejs.com/), [@okikio/animate](http://npmjs.com/@okikio/animate), [motion one](https://motion.dev/), [framer motion](https://www.framer.com/docs/animation/), etc...) or the [Web Animation API (WAAPI)](https://developer.mozilla.org/en-US/docs/Web/API/Web_Animations_API/Using_the_Web_Animations_API), you can learn more in the [Usage](#use-with-animation-libraries) section. `spring-easing` works by generating arrays of `frame`'s which when placed in linear order creates a smooth spring like animation. > A `frame` represent a single frame of an animation > _**Note**: the `spring-easing` package also supports 4 extra variants of [`spring`](https://spring-easing.okikio.dev/functions/SpringFrame), namely [`spring-in`](https://spring-easing.okikio.dev/functions/SpringInFrame), [`spring-out`](https://spring-easing.okikio.dev/functions/SpringOutFrame), [`spring-out-in`](https://spring-easing.okikio.dev/functions/SpringOutInFrame), and [`spring-in-out`](https://spring-easing.okikio.dev/functions/SpringInOutFrame), you can use these easing to create some really unique spring like animations._ You can create animation's like this with `spring-easing`, A demo of the various spring-easings available > _Check out the spring easing variants on [Codepen](https://codepen.io/okikio/pen/MWEMEgJ)._ > _**Attention**: This entire library is a lightweight version of the [`CustomEasing`](https://native.okikio.dev/animate/api/custom-easing/) implemented in [`@okikio/animate`](https://native.okikio.dev/animate), which supports only string and number interpolation. If you'd like the complete `CustomEasing` with color interpolation, complex value interpolation, and more, go through the source code as a [Github Gist](https://gist.github.com/okikio/bed53ed621cb7f60e9a8b1ef92897471#file-custom-easing-ts), which is licensed under the MIT license._ ## Installation ### Node ```bash npm install spring-easing ```
Others ```bash yarn add spring-easing ``` or ```bash pnpm install spring-easing ```
### Deno ```ts import { SpringEasing } from "https://deno.land/x/spring_easing/mod.ts"; ``` ## Usage ```ts import { SpringEasing } from "spring-easing"; // or import SpringEasing from "spring-easing"; ``` You can also use it directly through a script tag: ```html ``` You can also use it via a CDN, e.g. ```ts import { SpringEasing } from "https://esm.run/spring-easing"; // or import { SpringEasing } from "https://esm.sh/spring-easing"; // or import { SpringEasing } from "https://unpkg.com/spring-easing"; // or import { SpringEasing } from "https://cdn.skypack.dev/spring-easing"; // or import { SpringEasing } from "https://deno.bundlejs.com/file?q=spring-easing"; // or any number of other CDN's ``` ### Use with Animation Libraries > _**Note:** I cannot guarantee that every animation library works with `spring-easing`, for example, if an animation library doesn't support array values as keyframes, it won't work well with `spring-easing`._ The libraries that have been tested are: | Animation Library | Support | Demo | | ------------------------------------------------------------------------------------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------ | | [GSAP](https://greensock.com/) | ✅ Yes - [Wrap Method]() | [Codepen](https://codepen.io/okikio/pen/MWEMEgJ) | | [animejs](https://animejs.com) | ✅ Yes - [Array Keyframes](https://animejs.com/documentation/#animationKeyframes) | [Codepen](https://codepen.io/okikio/pen/MWEMEgJ) | | [Framer Motion](https://www.framer.com/motion/) | ✅ Yes - [Array Keyframes](https://www.framer.com/docs/animation/##keyframes) | [Codepen](https://codepen.io/okikio/pen/MWEMEgJ) | | [Motion One](https://motion.dev) | ✅ Yes - [Array Keyframes](https://motion.dev/dom/animate#keyframes) | [Codepen](https://codepen.io/okikio/pen/MWEMEgJ) | | [@okikio/animate](https://okikio.github.io/native/packages/animate) | ✅ Yes - [Array Keyframes](https://okikio.github.io/native/packages/animate/#animations) | [Codepen](https://codepen.io/okikio/pen/MWEMEgJ) | | [Web Animation API (WAAPI)](https://developer.mozilla.org/en-US/docs/Web/API/Web_Animations_API) | ✅ Yes - [Array Keyframes](https://developer.mozilla.org/en-US/docs/Web/API/Web_Animations_API/Keyframe_Formats#:~:text=An-,object,-containing%20key%2Dvalue) | [Codepen](https://codepen.io/okikio/pen/MWEMEgJ) | | [Linear Easing (CSS)](https://linear-easing-generator.netlify.app) | ✅ Yes - [CSS Spring Easing](#CSSSpringEasing) | [Codepen](https://codepen.io/okikio/pen/MWEMEgJ) | | [Linear Easing (WAAPI)](https://linear-easing-generator.netlify.app) | ✅ Yes - [CSS Spring Easing](#CSSSpringEasing) | [Codepen](https://codepen.io/okikio/pen/MWEMEgJ) | e.g. ```ts import anime from "animejs"; import { SpringEasing, SpringOutFrame } from "spring-easing"; // Note: this is the return value of `SpringEasing` and `GenerateSpringFrames` let [translateX, duration] = SpringEasing([0, 250], { easing: "spring-out-in(1, 100, 10, 0)", // You can change the size of Array for the SpringEasing function to generate numPoints: 200, // The number of decimal places to round, final values in the generated Array // This option doesn't exist on `GenerateSpringFrames` decimal: 5, }); anime({ targets: "div", // Using spring easing animate from [0 to 250] using `spring-out-in` translateX, // You can interpolate between strings // You can set the easing without an easing options object // You can interpolate between more than 2 values // Remember the `0` index of `SpringEasing` is an array of spring animation keyframes rotate: SpringEasing( ["0turn", 1, 0, 0.5], [SpringOutFrame, 1, 100, 10, 0] )[0], // TIP... Use linear easing for the proper springy effect easing: "linear", // The optimal duration for this specific spring configuration, e.g. mass, velocity, damping, etc... duration, }); ``` Or ```ts import { CSSSpringEasing } from "spring-easing"; let [easings, duration] = CSSSpringEasing({ easing: "spring-out-in(1, 100, 10, 0)", // The number of decimal places to round to decimal: 5, }); document.querySelector('div').animate({ // Using spring easing animate from [0 to 250] using `spring-out-in` translate: ["0", "250px"], // You can interpolate between strings // You can set the easing without an easing options object // You can interpolate between more than 2 values // Remember the `0` index of `SpringEasing` is an array of spring animation keyframes rotate: ["0turn", "1turn", "0turn", "0.5turn"], }, { // TIP... Use linear easing for the proper springy effect easing: `linear(${easings})`, // The optimal duration for this specific spring configuration, e.g. mass, velocity, damping, etc... duration, }); ``` > _**Note**: make sure to read the comments above, as they are valuable resources for understanding what is happening._ > Check out this demo on [Codepen](https://codepen.io/okikio/pen/MWEdzNg) ## Showcase A couple sites/projects that use `spring-easing`: - [`postcss-spring-easing`](https://github.com/okikio/postcss-spring-easing) - Your site/project here... ## API
What's New... > **`NEW`** CSS Spring Easing & support for the `linear()` easing function > > ### CSSSpringEasing > > Generates a string that represents a set of values used with the linear-easing function to replicate spring animations, > you can check out the linear-easing playground here https://linear-easing-generator.netlify.app/ > Or check out a demo on Codepen https://codepen.io/okikio/pen/vYVaEXM > > CSS Spring Easing has 4 properties they are `easing` (all spring frame functions are supported), `numPoints` (the size of the Array the frmae function should create), `decimal` (the number of decimal places of the values within said Array) and `quality` (how detailed/smooth the spring easing should be).. > > | Properties | Default Value | > | ----------- | ----------------------- | > | `easing` | `spring(1, 100, 10, 0)` | > | `numPoints` | `50` | > | `decimal` | `3` | > | `quality` | `0.85` | > > `CSSSpringEasing` is meant to be used with the `linear-easing()` function to replicate spring animations. > It is based on the work done by [Jake Archibald](https://github.com/jakearchibald) in his [Linear Easing Generator](https://github.com/jakearchibald/linear-easing-generator). > > > **Note**: This feature will only work on versions of browsers from ~a month ago (`Chrome & Edge 113`, and `Firefox 112`) except for `Safari` which doesn't support it yet. > > ```ts > import { CSSSpringEasing } from "spring-easing"; > > let [easing, duration] = CSSSpringEasing({ > easing: "spring-out-in(1, 100, 10, 0)", > > // You can change the size of Array for the SpringEasing function to generate > numPoints: 200, > > // The number of decimal places to round, final values in the generated Array > // This option doesn't exist on {@link GenerateSpringFrames} > decimal: 5, > > // How detailed/smooth the spring easing should be > // 0 means not smooth at all (shorter easing string) > // 1 means as smooth as possible (this means the resulting easing will be a longer string) > quality: 0.85, > }); > > document.querySelector("div").animate( > { > translate: ["0px", "250px"], > rotate: ["0turn", "1turn", "0turn", "0.5turn"], > }, > { > easing: `linear(${easing})`, > > // The optimal duration for this specific spring > duration, > } > ); > ``` > > > **Note**: You can also use custom easings with `CSSSpringEasing` e.g. > > ```ts > import { > CSSSpringEasing, > limit, > registerEasingFunctions, > } from "spring-easing"; > > registerEasingFunctions({ > bounce: (t) => { > let pow2: number, > b = 4; > while (t < ((pow2 = Math.pow(2, --b)) - 1) / 11) {} > return ( > 1 / Math.pow(4, 3 - b) - 7.5625 * Math.pow((pow2 * 3 - 2) / 22 - t, 2) > ); > }, > elastic: (t, params: number[] = []) => { > let [amplitude = 1, period = 0.5] = params; > const a = limit(amplitude, 1, 10); > const p = limit(period, 0.1, 2); > if (t === 0 || t === 1) return t; > return ( > -a * > Math.pow(2, 10 * (t - 1)) * > Math.sin( > ((t - 1 - (p / (Math.PI * 2)) * Math.asin(1 / a)) * (Math.PI * 2)) / p > ) > ); > }, > }); > > CSSSpringEasing("bounce"); // ["0, 0.013, 0.015, 0.006 8.1%, 0.046 13.5%, 0.06, 0.062, 0.054, 0.034, 0.003 27%, 0.122, 0.206 37.8%, 0.232, 0.246, 0.25, 0.242, 0.224, 0.194, 0.153 56.8%, 0.039 62.2%, 0.066 64.9%, 0.448 73%, 0.646, 0.801 83.8%, 0.862 86.5%, 0.95 91.9%, 0.978, 0.994, 1", ...] > CSSSpringEasing("elastic(1, 0.5)"); // ["0, -0.005 32.4%, 0.006 40.5%, 0.034 51.4%, 0.033 56.8%, 0.022, 0.003, -0.026 64.9%, -0.185 75.7%, -0.204, -0.195, -0.146, -0.05, 0.1 89.2%, 1", ...] > ``` > > ### getOptimizedPoints > > This function generates an optimized set of points to be used with the `linear-easing()` function > using the Ramer-Douglas-Peucker algorithm and rounds the x and y values of the resulting points. > > ```ts > import { getOptimizedPoints } from "spring-easing"; > > const points = [ > [0, 0], > [0.1, 0.2], > [0.5, 1], > [0.9, 0.2], > [1, 0], > ]; > const round = 2; > const simplify = 0.1; > > console.log(getOptimizedPoints(points, simplify, round)); //= [[0, 0], [0.5, 1], [1, 0]] > ``` > > ### getLinearSyntax > > This function converts a given set of points into an array of strings in a this format `["value percent%", ...]` e.g. `["0", "0.25 13.8%", "0.6 45.6%", "0.1", "0.4 60%", ...]`. > It's used to generate the syntax for the `linear-easing` function. > > ```ts > import { getLinearSyntax } from "spring-easing"; > > const points = [ > [0, 0], > [0.1, 0.2], > [0.5, 1], > [0.9, 0.2], > [1, 0], > ]; > const round = 2; > > console.log(getLinearSyntax(points, round)); //= [ '0', '0.2 10%', '1', '0.2 90%', '0' ] > ``` > **`RE-INSTATED`** _Added batch version of `SpringEasing` and the Interpolation functions which use a new syntax._ > > _The other version of `spring-easing` interpolation functions follow this syntax `(t, values, decimal) => string | number | any`, batch interpolation function use this new syntax `(arr_t, values, decimal) => string[] | number[] | any[]`._ > > _The key difference between both syntaxes are the parameters each function takes and the return value of each function._ > > _The older syntax returned instantaneous frame values at a specific t-value, but the new syntax returns all the frames that make the entire animation, allowing for performance optimizations that couldn't be done before._ > > _For the most part this shouldn't leave too much of an effect, but for those high-perf. applications this new batch synatax should prove useful._ > e.g. > > ```ts > function batchInterpolateNumber( > arr_t: number[], > values: number[], > decimal = 3 > ) { > // nth index > const n = values.length - 1; > > return arr_t.map((t) => { > // The current index given t > const i = limit(Math.floor(t * n), 0, n - 1); > > const start = values[i]; > const end = values[i + 1]; > const progress = (t - i / n) * n; > > return toFixed(scale(progress, start, end), decimal); > }); > } > > BatchSpringEasing([0, 250], `spring`, batchInterpolateNumber); > ``` > **`RE-INSTATED`** _There is a new `toAnimationFrames` function that converts interpolation functions written in this style `(t, values, decimal) => { ... }` to work in `BatchSpringEasing`._ > e.g. > > ```ts > import { > BatchSpringEasing, > toAnimationFrames, > toFixed, > scale, > limit, > } from "spring-easing"; > > function interpolateNumber(t: number, values: number[], decimal = 3) { > // nth index > const n = values.length - 1; > > // The current index given t > const i = limit(Math.floor(t * n), 0, n - 1); > > const start = values[i]; > const end = values[i + 1]; > const progress = (t - i / n) * n; > > return toFixed(scale(progress, start, end), decimal); > } > > function interpolatePixels(t: number, values: number[], decimal = 3) { > const result = interpolateNumber(t, values, decimal); > return `${result}px`; > } > > BatchSpringEasing([0, 250], "spring", toAnimationFrames(interpolatePixels)); > ``` > **`NEW`** _Optimized perf. of spring generation w/ help from [@jakearchibald](https://twitter.com/jaffathecake)_ > **`NEW`** _`mass`, `stiffness`, `damping`, and `velocity` now have a smaller minimum limit of `0.0001` instead of `0.1`_ > **`REVERT`** _The new interpolation syntax has been reverted and removed; `instantNumber`, etc... functions have been renamed to `interpolateNumber`, etc..._ > **`NEW`** _Re-introduced instantaneous interpolation functions._ > e.g. > > ```ts > import { > interpolateNumber, > interpolateString, > interpolateSequence, > interpolateComplex, > } from "spring-easing"; > ``` > > These functions represent the interpolated value at a specific instance in time, where time is represented by `t` with a range of `0` to `1`. > You can use these functions as building blocks to create your own custom interpolation functions. > **`NEW`** _(deprecated) `interpolateUsingIndex` is now an alias of `interpolateSequence`, it still keeps the same functionality._ > The recommendation is to use `interpolateSequence` instead of `interpolateUsingIndex`, but you can still keep using `interpolateUsingIndex`, but beware it can be removed in future versions. > **`NEW`** _Re-introduced instantaneous interpolation functions._ > e.g. > > ```ts > import { > instantNumber, > instantString, > instantSequence, > instanceComplex, > } from "spring-easing"; > ``` > > These functions represent the interpolated value at a specific instance in time, where time is represented by `t` with a range of `0` to `1`. > You can use these functions as building blocks to create your own custom interpolation functions. > > > **`BREAKING CHANGE`** _Interpolation functions use a new syntax._ > > _In older versions of `spring-easing` interpolation functions used to follow a syntax called the instantaneous interpolation function `(t, values, decimal) => string | number | any`, the new syntax is called interpolation function `(frames, values, decimal) => string[] | number[] | any[]`._ > > _The key difference between both syntaxes are the parameters each function takes and the return value of each function._ > > _The older syntax returned instantaneous frame values at a specific t-value, but the new syntax returns all the frames that make the entire animation, allowing for performance optimizations that couldn't be done before._ > > _For the most part this shouldn't leave too much of an effect as all the built-in interpolation functions have been updated to use the new synatax._ > e.g. > > ```ts > function interpolateNumber(frames: number[], values: number[], decimal = 3) { > // nth index > const n = values.length - 1; > > return frames.map((t) => { > // The current index given t > const i = limit(Math.floor(t * n), 0, n - 1); > > const start = values[i]; > const end = values[i + 1]; > const progress = (t - i / n) * n; > > return toFixed(scale(progress, start, end), decimal); > }); > } > > SpringEasing([0, 250], `spring`, interpolateNumber); > ``` > > > **`NEW`** _There is a new `toAnimationFrames` function that be used on instantaneous interpolation functions, to transform them into complete animation interpolation functions._ > e.g. > > ```ts > import { > SpringEasing, > toAnimationFrames, > toFixed, > scale, > limit, > } from "spring-easing"; > > function interpolateNumber(t: number, values: number[], decimal = 3) { > // nth index > const n = values.length - 1; > > // The current index given t > const i = limit(Math.floor(t * n), 0, n - 1); > > const start = values[i]; > const end = values[i + 1]; > const progress = (t - i / n) * n; > > return toFixed(scale(progress, start, end), decimal); > } > > function interpolatePixels(t: number, values: number[], decimal = 3) { > const result = interpolateNumber(t, values, decimal); > return `${result}px`; > } > > SpringEasing([0, 250], "spring", toAnimationFrames(interpolatePixels)); > ``` > > > **`NEW`** _Easily register new easing functions._ > e.g. > > ```ts > import { SpringEasing, registerEasingFunction } from "spring-easing"; > > registerEasingFunction("linear", (t) => t); > registerEasingFunctions({ > quad: (t) => Math.pow(t, 2), > cubic: (t) => Math.pow(t, 3), > }); > > SpringEasing([0, 250], "linear"); > > SpringEasing([0, 250], "quad"); > ``` > **`NEW`** _SpringEasing now support interpolating between strings. It treats the units of the first value as the units for the rest of the values to interpolate between._ > e.g. > > ```ts > SpringEasing(["0turn", "1px", "18rem", "125deg", 25], ...) > ``` > > _**Important** All the values above get transformed to `["0turn", "1turn", "18turn", "125turn", "25turn"]`, before being interpolated._ > **`NEW`** _`interpolateStrings`, `interpolateUsingIndex`, and `interpolateComplex`, are now built-in, they allow for supporting string keyframes._ > **`NEW`** _Custom interpolation functions are now supported._ > e.g. > > ```ts > import { interpolateNumber, toFixed, scale, limit } from "spring-easing"; > // ... > export function interpolateColor(t: number, values: string[], decimal = 3) { > const color = transpose(...values.map((v) => rgba(v))).map( > (colors: number[], i) => { > const result = interpolateNumber(t, colors); > return i < 3 ? Math.round(result) : toFixed(result, decimal); > } > ); > > return `rgba(${color.join()})`; > } > > SpringEasing(["red", "green", "#4f4"], "spring", interpolateColor); > ``` > > _**Important** The logic for color interpolation is defined in this [tests/utils/interpolate-color.ts](https://github.com/okikio/spring-easing/blob/main/tests/utils/interpolate-color.ts)._
The API of `spring-easing` is pretty straight forward, the `SpringEasing` function generates an array of values using a frame functions, which in turn creates the effect of spring easing. To use this properly make sure to set the easing animation option to "linear". Check out a demo of `SpringEasing` at `SpringEasing` has 3 properties they are `easing` (all the easings from [EasingFunctions](https://spring-easing.okikio.dev/variables/easingfunctions) are supported on top of frame functions like `SpringFrame`, `SpringFrameOut`, etc..), `numPoints` (the size of the Array the frame function should create), and `decimal` (the number of decimal places of the values within said Array). | Properties | Default Value | | ----------- | ----------------------- | | `easing` | `spring(1, 100, 10, 0)` | | `numPoints` | `50` | | `decimal` | `3` | By default, Spring Easing support easings in the form, | constant | accelerate | decelerate | accelerate-decelerate | decelerate-accelerate | | :------- | :----------------- | :--------- | :-------------------- | :-------------------- | | | spring / spring-in | spring-out | spring-in-out | spring-out-in | All **Spring** easing's can be configured using theses parameters, `spring-*(mass, stiffness, damping, velocity)` Each parameter comes with these defaults | Parameter | Default Value | | --------- | ------------- | | mass | `1` | | stiffness | `100` | | damping | `10` | | velocity | `0` | To understand what each of the parameters of `SpringEasing` mean and how they work I suggest looking through the [SpringEasing API Documentation](https://spring-easing.okikio.dev/functions/springeasing) > _**Note:** the return value of the `SpringEasing` function is actually `[Array of keyframes, duration]`, in that order._ For a full understanding of what is happening in the library, pleace check out the [API site](https://spring-easing.okikio.dev/modules) for detailed API documentation. ## Browser Support | Chrome | Edge | Firefox | Safari | IE | | ------ | ---- | ------- | ------ | --- | | 4+ | 12+ | 4+ | 4+ | 10+ | Native support for `spring-easing` is great as it doesn't use any browser specific or nodejs specific API's, you should be good to use `spring-easing` in any environment. > Note: `CSSSpringEasing` is meant for browsers which have support for the `linear()` easing function, > which as of right now is `Chrome & Edge 113` + `Firefox 112`, Safari doesn't support it yet. ## Contributing I encourage you to use [pnpm](https://pnpm.io/configuring) to contribute to this repo, but you can also use [yarn](https://classic.yarnpkg.com/lang/en/) or [npm](https://npmjs.com) if you prefer. Install all necessary packages ```bash npm install ``` Then run tests ```bash npm test ``` Build project ```bash npm run build ``` Preview API Docs ```bash npm run typedoc && npm run preview ``` > _**Note**: this project uses [Conventional Commits](https://www.conventionalcommits.org/en/v1.0.0/) standard for commits, so, please format your commits using the rules it sets out._ ## License See the [LICENSE](./LICENSE) file for license rights and limitations (MIT). The `CSSSpringEasing`, `getOptimizedPoints` and `getLinearSyntax` function are based of the work done by [Jake Archibald](https://github.com/jakearchibald/linear-easing-generator) in his [Linear Easing Generator](https://linear-easing-generator.netlify.app/) and are thus licensed under the [Apache License 2.0](https://github.com/jakearchibald/linear-easing-generator/blob/main/LICENSE).