To the point of being: Modify bootstrap-datepicker.js file
The code copy is as follows:
var zIndex = parseInt(this.element.parents().filter(function(){
return $(this).css('z-index') !== 'auto';
}).first().css('z-index')) +10;
Change +10 to +99999999;
Reason: z-index sets the stacking order of elements, from negative to positive means stacking from bottom to top. Here, use the css method to set z-index to 10, and it is an in-line style. It cannot be modified with a style sheet.
Summary: The method is very simple, but the process of finding the cause is very complicated. I searched here for a long time before I found a relatively simple solution. Friends who have the same needs will refer to it. I hope you like it.