if I want to get x by y?

[luther-nwpu]

I need this function。

[gre]

There is not a single solution to this problem, bezier curve is not a bijection.

That said, it only happens when one of the handle goes out of [0,1] on the y axis.

So what you can do is simply switch x and y of the bezier parameter and I think you get the reverse function

[housseynCheriet]

Best explanation of easing function
https://www.selectionjs.com/animation

[zikaari]

I also need to resolve x from y.

So what you can do is simply switch x and y of the bezier parameter and I think you get the reverse function

I tried but no luck, do I also need to invert/adjust some other parameters?

EDIT

Looked at the the code more closely - just need to swap the position of first 2 arguments and last 2 arguments to bezier function and then call the returned function with the y that you need the x for.

// resolve y
const interpolate = bezier(0.4, 0, 0.6, 1)

// resolve x
const uninterpolate =  bezier(0, 0.4, 1, 0.6)

const x = 0.25
const y = interpolate(x)

uninterpolate(y) === x  // true