ScrollBehavior definition is missing 'instant' for window.scrollTo

[RandScullard]

Bug Report

?? Search Terms

instant
ScrollBehavior
window
scrollTo
type definition

?? Version & Regression Information

v4.5.4, but it's also mentioned in #46654 (v4.4.4) and #28755 (v3.2.1)

? Playground Link

Playground link with relevant code

?? Code

window.scrollTo({
  top: 0,
  left: 0,
  behavior: 'instant' // This should be allowed
})

?? Actual behavior

The value of instant cannot be assigned to behavior when using window.scrollTo.

?? Expected behavior

The value of instant is allowed when using window.scrollTo according to https://developer.mozilla.org/en-US/docs/Web/API/Window/scrollTo as well as in real-world testing in major browsers. I just tested window.scrollTo with instant on Chrome, Firefox, and macOS Safari and it does not give the same behavior as auto. In my tests, auto produced smooth scrolling and instant scrolled instantly.

Please note that the MDN documentation specifies different behavior options for element.scrollTo and element.scrollIntoView vs. window.scrollTo. This bug report is specific to window.scrollTo. The existing ScrollBehavior type definition will most likely need to be bifurcated to handle all functions correctly.

Until the type definition is fixed, you can get the instant scrolling behavior by casting as any:

window.scrollTo({ top: 0, left: 0, behavior: 'instant' } as any)

[RandScullard]

Please note that this issue is very similar to #46654, but that issue was related to element.scrollTo and this issue is related to window.scrollTo. The two functions have different options for ScrollBehavior. (And thanks to @patik - his work on #46654 saved me time in creating this issue!)

[BayanBennett]

Note that behavior: "auto" inherits the behavior from the CSS scroll-behavior, which is why having the "instant" value is important

[BayanBennett]

Seems like there's another task for this:

• window.scrollTo behavior option missing "instant" string literal union TypeScript-DOM-lib-generator#1195

[BayanBennett]

More context: It seems like the "instant" value isn't part of the CSSOM spec https://github.com/w3c/csswg-drafts/blob/main/cssom-view-1/Overview.bs#L407

EDIT: instant is back due to w3c/csswg-drafts#8107, thanks to #47441 (comment) for pointing this out.

[zhangenming]

auto and instant behave differently in my browser

[YahangWu]

This has been restored in cssom w3c/csswg-drafts#8107, please added it back. Thanks :))

[curtisburns]

Just encountered this issue. Would be great to have this as MDN docs seem to suggest it is an option, and I only get the behaviour I need with instant and not auto which seems to fall back on the CSS style rule if set (I have it set to smooth). Have used 'instant' as ScrollBehavior in the meantime. Cheers.

[Teamop]

it's already fixed in #53133 which was just include in v5.1-beta

[cbroomemktw]

@Teamop thanks! For anyone who can't update while still in beta you can brute force this setting as a workaround:

      const scrollToOptions = { top: 0, left: 0, behavior: 'instant' };
      window.scrollTo(scrollToOptions as unknown as ScrollToOptions);

[DanielRuf]

Note that behavior: "auto" inherits the behavior from the CSS scroll-behavior, which is why having the "instant" value is important

Exactly.

[jakebailey]

As noted in #47441 (comment), this is already fixed and now released in TS 5.1.

[helloint]

As noted in #47441 (comment), this is already fixed and now released in TS 5.1.

Can this small issue being published to latest 4.x? Upgrading to 5.x is a big change to the project and the entire eco