AG Grid de-select 100 rows

Question

I am trying to do the following , select 100 rows and de-select the same 100 rows in AG Grid. Selecting 100 rows ( filtered/not) is working with the below

HTML :

<ag-grid-angular
style="width: 100%; height: 550px;"
class="ag-theme-material"
[rowData]="rowData"
[columnDefs]="columnDefs"
[enableSorting]="true"
[enableFilter]="true"
enableColResize="true"
[context]="mycontext"
pagination="true"
[rowSelection]="'multiple'"
[getRowNodeId]="getRowNodeId"
(selectionChanged) = "onSelectionChanged($event)">
</ag-grid-angular>

TS :

 {
headerName: '', field: 'random', width:50,
headerCheckboxSelection: true,
headerCheckboxSelectionFilteredOnly: true,
suppressRowClickSelection: true,
checkboxSelection: true}

  onSelectionChanged(params){    
  
  var selected = params.api.getSelectedRows().length;
  var totalRows = params.api.getDisplayedRowCount()
  console.log('selected',selected,'totalRows',totalRows)
  if(selected === totalRows){
    params.api.deselectAll()
    for (var i=0 ; i<=100;i++){
params.api.getDisplayedRowAtIndex(i).setSelected(true)
   }
  }
 }

But on the page when I try to uncheck checkbox header it is not hppening , Onselectionchanged triggered again and the same function executes , I am not able to clear the existing selection. Any help please ?