How to determine whether a checkbox is checked or not in Vue js

You can do something like:

if(this.rolesSelected != "") {
   alert('isSelected');
}

or v-on:click="samplefunction({{$role->id}},$event)"

samplefunction : function(value,event) {
    if (event.target.checked) {
       alert('isSelected');
    }
}

This worked for me.

<input type="checkbox" :id="poid" class="unchecked" name="single_select" ref="rolesSelected">

function (){
  if(this.$refs.rolesSelected.checked == false) {
    //do something
  }
}

function (){
  if(this.$refs.rolesSelected.checked == true) {
    //do something
  }
}