The FlexGridFilter extension (wijmo.grid.filter.js) allows you to add a filtering UI to the FlexGrid control.
The filtering UI adds filter icons to the column headers of the grid. Clicking the icons brings up an editor where user can select the values to be displayed (value filter) or they can set up conditions that must be satisfied by the values (condition filter).
You may also customize the filter to show a specific type of filter on each column, as shown in the case of Revenue column of this sample.