multiple selection in dropdown

Question

Hello guys, I want to select multiple values from dropdown list using comma seperated.i m attaching code .plz help me with this.

I am getting output as

,java

,net

 

That' my function

$scope.getKeySkills = function(value) {
if(value==null){
console.log(value);
$scope.form.data.keySkills = value;
}
else{
$scope.form.data.keySkills = ","+value;
}}
<div class="col-xl-4 col-lg-6 col-md-12 col-sm-12 col-12 mb-2">
<label for="validationCustom02">Key skills</label> <font
color="red">*</font> <select class="form-control inline"
ng-model="form.keySkill"
ng-change="getKeySkills(form.keySkill)"
ng-options="s.name as s.name for s in form.preload.keySkillsList"
required style="cursor: pointer" id="basic">
<option value="">--Key skills--</option>
</select>
<div class="valid-feedback">Looks good!</div>
</div>
<input type="hidden" ng-model="form.id" value="form.data.id">
<div class="col-xl-4 col-lg-6 col-md-12 col-sm-12 col-12 mb-2">
<label for="validationCustom01">key skills value</label><font
color="red">*</font> <input type="text" class="form-control"
id="validationCustom01" placeholder="values" value=""
ng-change="getKeySkills(form.keySkill)" ng-model="form.keySkill">
<div class="valid-feedback">Looks good!</div>
</div>