I have a code in view where i am opening a dialog and using a autofcous and a call to the method so it can call that method and add the code to the elements

i have it working by using setTimeout but i do not want to use setTimeout and make it workj with either computed or mounted so it can add elements to it, if i use mounted or computed, i get an error

async mounted() {
    await this.$nextTick();
    this.handleOpen();
  }

TypeError: Cannot read properties of null (reading 'setAttribute')

my working is here in the below fiddle

https://jsfiddle.net/ufdxhzkn/

the above fiddle actually works with settimeout, but does not work with mounted or computed, i do not want to use setTimeout, it should handle automatically and add relevant code when the popup is either rendered or opened.