Created
August 24, 2021 07:58
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/** | |
* @callback Tween | |
* @param {number} x | |
* @returns {number} | |
*/ | |
/** | |
* @callback Easing | |
* @param {number} x | |
* @returns {number} | |
*/ | |
/** | |
* @param {Easing} [easing] | |
* @returns {Tween} | |
*/ | |
export default function createTween(x0 = 0, x1 = 1, y0 = 0, y1 = 1, easing) { | |
const k = (y1 - y0) / (x1 - x0) | |
const b = (x1 * y0 - x0 * y1) / (x1 - x0) | |
if (easing !== undefined) { | |
const dx = x1 - x0 | |
return (x) => { | |
if (x <= x0) return y0 | |
if (x >= x1) return y1 | |
x = easing((x - x0) / dx) * dx + x0 | |
return k * x + b | |
} | |
} | |
return (x) => { | |
if (x <= x0) return y0 | |
if (x >= x1) return y1 | |
return k * x + b | |
} | |
} | |
// Paste more easings from https://easings.net/ | |
/** @type {Easing} */ | |
export const easeInExpo = (x) => (x === 0 ? 0 : Math.pow(2, 10 * x - 10)) | |
/** @type {Easing} */ | |
export const easeOutExpo = (x) => (x === 1 ? 1 : 1 - Math.pow(2, -10 * x)) |
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