Why is the icon not displayed on the left side of the drop-down box in bootstrap table?

problem description

the drop-down box in bootstrap table does not show the icon on the left

the environmental background of the problems and what methods you have tried

related codes

/ / Please paste the code text below (do not replace the code with pictures)
striped: true, / / interlaced discoloration

                cache: false, //true*
                pagination: false, //*
                sortable: true, //
                // sortOrder: "asc", //
                sidePagination: "client", //:clientserver*
                pageNumber: 1, //
                pageSize: 25, //*
                pageList: [10, 25, 50], //*
                search: false, //
                searchOnEnterKey: true,
                trimOnSearch: true,
                strictSearch: true,
                showColumns: true, //
                showRefresh: false, //
                minimumCountColumns: 2, //
                clickToSelect: false, //
                // height: 500, //height
                uniqueId: "id", //
                showToggle: false, //
                cardView: false, //
                detailView: false, //
                showExport: true,  //
                buttonsAlign: "right",
                exportTypes: ["excel", "txt", "doc"],  //
                Icons: "glyphicon-export",
                exportDataType: "all",             //basic", "all", "selected".
                exportOptions: {
                    //ignoreColumn: [0],  //
                    fileName: $("-sharpdatetimepicker").val() + "",  //
                    worksheetName: "sheet1",  //
                    tableName: $("-sharpdatetimepicker").val() + "",
                    excelstyles: ["background-color", "color", "font-size", "font-weight", "border-top"]
                },
                onLoadSuccess: function () {
                }
            });
        });![][1]

what result do you expect? What is the error message actually seen?

Css
Sep.02,2021

which css? have you loaded If the basic functionality is correct, but the icon is not displayed correctly, it is usually because the css is not loaded correctly.

MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1b3920b-2c179.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1b3920b-2c179.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
Need Help?