Return results for results which include the variable in the array in VueJS/JS

Question

I have a issue whereby my results will return if I match one of the months in my array ie. 'April'. The issue I have is that my result wont return if the startdate output has multiple months i.e (Jan, Feb, April)

Can anyone help? I hope I have provided enough info below.

<h3 class="pt-4">Start month</h3>
      <ul
        v-for="startdate in uniquestartdate"
        :key="startdate"
        class="d-inline"
      >
        <li>
          <label class="pr-2">{{ startdate }}</label>
          <input type="checkbox" v-model="startdates" :value="startdate" />
        </li>
      </ul>

computed: {
 dataFilters() {
      this.updateURL();
      const filteredResults = this.results.filter((a) => {
       
        if (
          this.startdates.length &&
          !this.startdates.includes(a.startdate)
        )
return false;
  return true;
      });
      return filteredResults;
    },
}

methods: {  
          const startdate = this.results
            .filter((result) => result && result.startdate)
            .map((item) => item.startdate)
            .filter((startdate, i, arr) => arr.indexOf(startdate) === i);
          // Split multiple levels in strings and store in an array
          let startdate = [];
          startdate.forEach((item) => {
            const splitArr = item.split(", ");
            startdate = startdate.concat(splitArr).sort();
          });

          // Filter again for unique 
          this.uniquestartdate = startdate.filter(
            (startdate, i, arr) => arr.indexOf(startdate) === i
          );
          this.results.forEach((result) => {
            console.log(result.startdate);
          });

}

** The image below shows the output for 'this.results.forEach((result) => {
                console.log(result.startdate);'**