try this

changeInput (value) {
      console.log(this.$refs.editorval.$refs.content)
      const content = this.$refs.editorval.$refs.content
      if (content) {
        if (window.getSelection) { // ie11 10 9 ff safari
          var range = window.getSelection()
          console.log(range)
          this.cursorPosition = range.focusOffset
          console.log('cursorPos:', this.cursorPosition)
        }
        this.cursorPosition = 0
      }
    }