framer-motion
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A simple and powerful JavaScript animation library
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JavaScript
import { warning, secondsToMilliseconds, millisecondsToSeconds } from 'motion-utils';
import { clamp } from '../../../utils/clamp.mjs';
import { springDefaults } from './defaults.mjs';
const safeMin = 0.001;
function findSpring({ duration = springDefaults.duration, bounce = springDefaults.bounce, velocity = springDefaults.velocity, mass = springDefaults.mass, }) {
let envelope;
let derivative;
warning(duration <= secondsToMilliseconds(springDefaults.maxDuration), "Spring duration must be 10 seconds or less");
let dampingRatio = 1 - bounce;
/**
* Restrict dampingRatio and duration to within acceptable ranges.
*/
dampingRatio = clamp(springDefaults.minDamping, springDefaults.maxDamping, dampingRatio);
duration = clamp(springDefaults.minDuration, springDefaults.maxDuration, millisecondsToSeconds(duration));
if (dampingRatio < 1) {
/**
* Underdamped spring
*/
envelope = (undampedFreq) => {
const exponentialDecay = undampedFreq * dampingRatio;
const delta = exponentialDecay * duration;
const a = exponentialDecay - velocity;
const b = calcAngularFreq(undampedFreq, dampingRatio);
const c = Math.exp(-delta);
return safeMin - (a / b) * c;
};
derivative = (undampedFreq) => {
const exponentialDecay = undampedFreq * dampingRatio;
const delta = exponentialDecay * duration;
const d = delta * velocity + velocity;
const e = Math.pow(dampingRatio, 2) * Math.pow(undampedFreq, 2) * duration;
const f = Math.exp(-delta);
const g = calcAngularFreq(Math.pow(undampedFreq, 2), dampingRatio);
const factor = -envelope(undampedFreq) + safeMin > 0 ? -1 : 1;
return (factor * ((d - e) * f)) / g;
};
}
else {
/**
* Critically-damped spring
*/
envelope = (undampedFreq) => {
const a = Math.exp(-undampedFreq * duration);
const b = (undampedFreq - velocity) * duration + 1;
return -safeMin + a * b;
};
derivative = (undampedFreq) => {
const a = Math.exp(-undampedFreq * duration);
const b = (velocity - undampedFreq) * (duration * duration);
return a * b;
};
}
const initialGuess = 5 / duration;
const undampedFreq = approximateRoot(envelope, derivative, initialGuess);
duration = secondsToMilliseconds(duration);
if (isNaN(undampedFreq)) {
return {
stiffness: springDefaults.stiffness,
damping: springDefaults.damping,
duration,
};
}
else {
const stiffness = Math.pow(undampedFreq, 2) * mass;
return {
stiffness,
damping: dampingRatio * 2 * Math.sqrt(mass * stiffness),
duration,
};
}
}
const rootIterations = 12;
function approximateRoot(envelope, derivative, initialGuess) {
let result = initialGuess;
for (let i = 1; i < rootIterations; i++) {
result = result - envelope(result) / derivative(result);
}
return result;
}
function calcAngularFreq(undampedFreq, dampingRatio) {
return undampedFreq * Math.sqrt(1 - dampingRatio * dampingRatio);
}
export { calcAngularFreq, findSpring };