jquery - How to show vertical scroll bar on select box -

i using angular select box ,i need show scroll bar if data more 5 .

<select class="form-control" data-ng-model='projectlistdata.appversion' ng-selected ng-options="v.version v.version v in versionlist | orderby:'-version' " >     <option value="" selected="selected" disabled="disabled">choose version</option> </select> 

i tried size not working .

size = '5' 

please suggest

html:

<select id="versions" class="form-control" data-ng-model='projectlistdata.appversion' ng-selected ng-options="v.version v.version v in versionlist | orderby:'-version' " >     <option value="" selected="selected" disabled="disabled">choose version</option> </select> 

js:

if($scope.versionlist.length > 5){     //vanilla js dropdown defined     var dropdown = document.getelementbyid("versions");     dropdown.style.overflow = "scroll";     //single line     document.getelementbyid("versions").style.overflow = "scroll";     //jquery     $("#versions").css("overflow", "scroll"); }