Closes #16151 by merging a rebased version of it that adds docs and 1 more assertion.

Closes #16039.

Erratum from #15496

Fixed performance bug where a tooltip element is created and then immediately destroyed when tooltip.hide() is called and there is no existing tooltip element

Resolves #15557 by merging it.

[Ref #15881] Use Explicit Values for javascript variables rather than chained ones.

From https://github.com/twbs/bootstrap/pull/15881#discussion_r25330647

isHorizontal => isVertical

Closes #15484

This reverts commit 1b323762.
This reverts PR #14189 because it caused major regressions.

Fixes #15168.

We'll try to revisit #14167's feature request in Bootstrap v4.

[skip validator]

Fixes #14375.
Closes #14519 by merging it.

Fixes #14167.
Closes #14189 by merging it.

Fixes #14756.
Closes #14767.

Fixes #14561. Big thanks to @wickstargazer.

[skip validator]

Fixes #14553.

Fixes #14322.
Closes #14581.

Fixes #13696.
Fixes #13696.
Fixes #14197.
Closes #13718.

Fixes #13031.

Fixes #14483

Closes #14093
Correction to #14090
Relevant docs: https://developer.mozilla.org/en-US/docs/Web/API/Element.getBoundingClientRect#Browser_compatibility

- is(':visible') seems to be the only reliable check, without a refactoring of how hoverState is used
- tests need improvement

[skip validator]

Fixes #14241

Will hopefully revert this reversion and land a fully-working version of UMD in v3.3.0.

Revert "some changes from #13801 - add strict mode back and =="
This reverts commit 2b302f69.

Revert "Fix regression of #10038 introduced by #13772"
This reverts commit e9d6756a.

Revert "MD/CommonJS/Globals #12909"
This reverts commit 1c6fa901.

Revert "address #13811"
This reverts commit f347d7d9.

Conflicts:
    js/carousel.js
    js/collapse.js
    js/dropdown.js
    js/modal.js
    js/tab.js
    js/tooltip.js

Closes #13782 by merging it.