BUG: scrollToTime 00h:00m doesn't work

[amok]

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Report a bug

What's the current behavior?

scrollToTime prop does not work if the value's date has 00h 00m

demo: https://codesandbox.io/embed/react-big-calendar-issue-scrolltotime-dp9zy
video: https://monosnap.com/file/dP5aEOh73L2K7Z7IfU2XJQtNnxdtJS

It mostly likely happens because of this check https://github.com/intljusticemission/react-big-calendar/blob/master/src/TimeGrid.js#L261 - scrollToTime is not being applied because this._scrollRatio is zero (false) (calculated at line https://github.com/intljusticemission/react-big-calendar/blob/master/src/TimeGrid.js#L275)

What's the expected behavior?

view scrolls to top when scrollToTime has been set to 00h:00m

[Dragomir-Ivanov]

Used your codesandbox as a template, and tried your issue. It seems to work fine with:

const stt00 = new Date(new Date().setHours(0, 0));
const stt10 = new Date(new Date().setHours(10, 0));

Not that in your code stt00 was new Date(new Date().setHours(0, 0, 0, 0));

[amok]

@Dragomir-Ivanov that's true
as I understand it happens because "shouldUpdate" is being calculated basing on milliseconds https://github.com/intljusticemission/react-big-calendar/blob/master/src/TimeGrid.js#L261

this._scrollRatio = diffMillis / totalMillis

when you setHours(hours, minutes) milliseconds value is not zero (with a high enough level of probability :) )
but when you setHours(hours, minutes, seconds, milliseconds) the value of milliseconds is always 0 so the bug exist.

[Dragomir-Ivanov]

@amok I didn't looked at the code, however your advice seems reasonable. In any case, explicit check for 0 will be needed. Perhaps you can make a PR?

[amok]

@Dragomir-Ivanov done. pls take a look at #1501

[Dragomir-Ivanov]

@amok Good work, mate!